Richard Garwin - Session I

Garwin:

Okay, it is Saturday, June 26th, 2004, and I am talking with Dan Ford. Let's see how this works.

Ford:

I guess we can start in Cleveland, Ohio, in 1928.

Garwin:

April 19, 1928 is as far back as I go, although I believe before that I traveled to New Orleans with my parents, but they only told me about it. I don't know.

Ford:

Where did your parents come from?

Garwin:

Well, it's more complicated than I was told when I grew up. My mother's family came from Hungary, and we could probably find the name of the town, but we didn't really pay much attention. She came when she was 12 years old, although she had told me — and I put it on my government clearance forms for many years — that she was born in the United States.

My father's family came from Poland, or Ukraine, or whatever it was at the time. For long after I learned that my mother was not born in the United States, which was sometime in the 1990s, I still thought my father was born in the United States — but I don't think he was [he was, indeed]. His mother and father took up residence in Chicago. His father had, I believe, a shoe store, and his — my father's father — was shot by his partner, shot and killed by his partner. Now, this is all hearsay. I don't know whether it's true or not. So my father's mother had four boys, and she put the two middle ones, I guess, in an orphanage. She moved from Chicago to Cleveland, Ohio, because there was a famous Jewish orphanage there called Bellefaire, on the east side of Cleveland.

So it was my father and his older brother Lou who were in the orphanage, and the oldest and youngest sons, Abe and Joe, were brought up by my grandmother. I didn't know my grandmother [my father’s mother] well. I think I met her only a couple of times, but I think she was unhappy that my father married my mother because she didn't come from a good society family or anything like that. But I did know all my uncles very well, and Abe… I think Dad was the only one who went to college. Lou was an intellectual. He was a socialist, or a communist. He also invented some things. I don't know that he ever made any money out of it.

Lois knew my family. We were married when we were — well in 1947, so very young, and had known one another for several years before that. So she spent a lot of time with my family and knew my uncles, some of my aunts on my father's side, and so on.

My mother had a much bigger family. Her parents, having come from Hungary, eventually had 11 or maybe 12 children, 9 of whom grew to adulthood. My mother I believe was the second oldest. They're all gone now, except for the two. I mentioned my Aunt Margie, who lives in Cleveland, and my Uncle Ken, who's younger — lives in Los Angeles. We used to see him every year, but last time we saw him, he was not in very good shape. We have only reports. We haven't talked to him recently.

My father graduated from Bellefaire, I guess. I think he went through maybe elementary school there — maybe high school. Then he went to Case, which was at that time Case School of Applied Science. In fact, when I went to Case in 1944, it was still Case School of Applied Science, but in short order it changed its name to Case Institute of Technology and then ultimately to Case Western Reserve University when it merged with Western Reserve University, which was the neighboring school.

Ford:

As far as your family is concerned, do you have documents, letters, photos, material like that?

Garwin:

Well, I have pictures of my parents and a few pictures of my mother's parents and some group pictures of her family. I have very few pictures of my father's brothers, and maybe one of his younger brother's wife and children. Probably have a picture of Lou and maybe of Abe. Abe ran stores, little stores, in Akron, Ohio, or someplace like that. Then after he retired, he came out here to San Diego and lived with Lou's son here. We visited them a number of times. Lou was divorced from his wife Celia and then married another woman, who's name I remember very well. She just died a couple of years ago. Just slipped my mind at the moment [Dorothy]. But Lou and Celia's daughter Judy was a good friend of Lois's in elementary school, and junior high, and high school. I was friendly with Judy as well, and she lives in Berkeley. She has several children. She married a man of Japanese parentage, and we're good friends with them, so we see them whenever we're in Northern California, as we were in March when I was visiting Professor Drell lecturer, I guess, at Stanford University. So we went over and Lois spent the day, and we had dinner with them.

My mother's family was religious. That is, her parents were Orthodox Jews. But the rest of the family was not observant at all. My parents never went to services. They did insist on sending me to Sunday school. I went under protest and did as little as possible.

Ford:

Jewish Sunday school?

Garwin:

Jewish Sunday school, right. They insisted I should either have a Bar Mitzvah or be confirmed, so I made the choice. I was confirmed, and Lois and I were in the same confirmation class, I guess.

Ford:

There's such a thing as Jewish confirmation?

Garwin:

Yeah. I don't know if there always is, but you know, it's kind of graduation from Sunday school. Then you can go on to further studies, but it's set at a level where people reach their — they get confirmed before they reach their level of tolerance, or whatever.

My mother's parents had these nine adult children, all of whom we knew very well. My father's parents had these four boys, whom I knew very well. I have one brother, and Lois has one brother. They're the same age. In fact, that's how she and I first got to know one another, because her younger brother Howard and my brother Edward… Ed was born in 1933; Howard maybe also. They were good friends, so Howard would come to our house to play when he was a little kid, and Lois's parents both worked. They ran a grocery store or whatever, so she would call up and ask us please to send Howard home so she could make his dinner.

Anyhow, I grew up in Cleveland, Ohio on Paxton Road, which was on the east side of Cleveland, but not nearly as far out as Bellefaire, which is in Cleveland Heights or beyond. There is the foothills of the Appalachians there, so the rise just east of Case Western Reserve University marks the boundary between Cleveland and Cedar Heights.

Ford:

How again did your father become orphaned?

Garwin:

His father was shot by his business partner when dad was seven years old, I'm told.

Ford:

What happened to his mother?

Garwin:

His mother was the one who had the four children, but you know, if you have a widowed mother with four children — she decided she couldn't keep all four. She kept two with her — the oldest and the youngest — and she sent the middle two to the orphanage. But to do so, she moved to Cleveland, where there was a much better orphanage than there was in Chicago.

Ford:

What was the family's name originally?

Garwin:

It was Gawronski, I believe. I have some books which show it. And the four boys all changed their names at the same time, probably in 1922 or so.

Ford:

They all changed it to Garwin?

Garwin:

Garwin, right.

Ford:

Your father went to the university?

Garwin:

Yes, he went to Case Western Reserve. He went to Case School of Applied Science — was not a university at that time. It gave only bachelor’s degrees. Maybe master’s degrees. I don't know. And he graduated in electrical engineering. I don't know exactly his job career. He never worked as an electrical engineer. He got a job as a high-school teacher of electricity at the East Technical High School in Cleveland. So he taught kids practical things and electrical theory. Then, in order to make more money, he had a job also as a motion-picture projectionist. Theaters were open on weekends and in the evenings, so that fit quite well. He was also involved in instructing projectionists how to handle the equipment. He taught them about optics.

I have a lot of photographs that he took of optical demonstrations where he made some lenses, two-dimensional lenses, and had smoke — he was a smoker — so you can see the beams of light as the light comes in a parallel beam from a point source. The condenser lens that makes the parallel beam, then goes through the film. The objective lens then focuses onto the screen. So he has very nice pictures of that type.

When sound came in in 1928, it was a whole new thing. You could see what the optics were doing, but you couldn't see what the sound was doing. So he had courses for the other projectionists to teach them how to deal with amplifiers. Initially, of course, there were records that were more or less synchronized with the film, but the complicated thing was sound on film, where in addition to the pictures laid out on the film strip, there is a separate little sound track, and that sound track has typically a wiggly line — black on the left side of it; clear on the other side — and a photocell, which looks at this uniformly moving strip of film in order to play back the sound.

[off-topic]

Ford:

You said your father made pictures? You mean photographs?

Garwin:

My father had a very nice camera, a film-pack camera so that the back came off, with a 4x5 inch format. He was a good photographer, so he would set things up on a tripod, arrange the lighting, and take pictures. He developed his own photographs, printed them all. When I was young, we built a darkroom so that we could do a good job on such things, and built the enlarger. He had a lot of lenses from old movie equipment. So, he was no longer a high-school teacher when I knew him.

Ford:

Do you have any of those pictures?

Garwin:

Yes, I have some. They're very pretty.

Ford:

Did he spend a lot of time teaching this stuff to you?

Garwin:

Yes, he was very available, and there were books around the house — handbooks, some of the textbooks he had used in college, and of course both my mother and father were big readers of mystery stories. So I was interested in these things. In the house on Paxton Road — I think was 928 Paxton Road — this was a two-family house. We had the second story. The first story was occupied by my mother's immediately younger sister Irene and her husband and their daughter. There was a basement in common and an attic. My father had the attic, and he had a little shop in there with a [wood] lathe, and we built an enormous electric train set. We made the tracks. Buying all that track was a lot of money, so it was a large-format train. Trains were about six-inches wide and very heavy, so it went from one room to another up there. Then when the Mahjong craze came along, my father and I made Mahjong sets for all the ladies. He had a rifle and a pistol, 22 caliber, so we did some target practice. One of our friends had a cottage on the lake west of Cleveland — Daniel Wasserman — and we would take the — they had some rifles too, so we'd go out there and shoot targets on the water and elsewhere. I was a pretty good shot.

Ford:

Did you go hunting?

Garwin:

No, never. I shot rats, occasionally. Probably not a good thing to do in a city, but I did it.

[off-topic]

Garwin:

We lived in that house until 1940. I don't recall when they moved into the house — I think before I was born or when I was born. In 1940, which was just at the end of the Depression, I believe that the house was worth less than the mortgage that needed to be paid off, so I think my parents walked away from it. Bought a brand new house in University Heights — 3817 Washington Boulevard in University Heights. A nice house. It was single-family. It had two floors, plus a basement and an attic, and a two-car garage set way back from the street.

Pretty soon my father had a room built on the back of the garage — somewhat bigger than a two-car garage — and he and his brother went into business installing sound equipment, motion picture equipment, for schools and businesses in the Cleveland area. It was just a little company. Initially the two of them, and then they hired a few more people to do this work. My mother did the office work. They bid, and they ordered equipment, and the equipment came, and they checked it out, installed it. On vacations sometimes I would go around with them and help install things in schools.

People were in stitches because my father and his brother Joe and I, and my brother Ed, all had voices that are essentially indistinguishable from one another. So they would see all these different looking people sounding exactly alike. Lois would call up and ask for Howard to be sent home, but she didn't know whether it was I or Joe or my dad that she was talking to.

Ford:

Were your parents political at all?

Garwin:

No, my parents were not political. My Uncle Lou was a very politically-minded person. I don't know that any of my family, on either side, was politically oriented. Lou's children, both David and Judy — both of whom went to the University of Chicago — were very political and probably still are. My mother, of course coming to the United States at the age of 12, spoke Hungarian only, but she learned English very rapidly. She didn't finish high school. I think she finished 10th grade, and she had a job. First she worked in the department store. Her boss told her — my mother's maiden name was Schwartz, her father was Samuel Schwartz, and her mother was Justine. Her boss told her, "You know Ms. Schwartz, when you go home on Friday, your English is very good. But you come back on Monday and we can hardly understand you." So she never spoke a word of Hungarian after that, to the extent that, as an older woman, she couldn't remember a word of Hungarian — which was a great loss. But then she became a legal secretary, a very good legal secretary. Her typing skills and shorthand stood her in good stead when she was helping —

Ford:

Your mother?

Garwin:

— my dad in his business. Right, because he would dictate. She would write it down on a shorthand pad. Or later on, she would just type it directly.

Her siblings were Selma, who was the oldest, my mother Leona, her sister Irene, then two other sisters, Sadie and Margie. Margie is still alive. The men were, from oldest to youngest… Well, I've forgotten the oldest. I know his name very well [Leo Schwartz]. Then Eugene, second oldest, and Nathan, and Ken. That should be five sisters and four brothers, if I've got it right.

Ford:

Lou was…?

Garwin:

Lou was my brother's brother. The oldest of the Schwartz brothers is a name I've forgotten. It'll come, and Lois knows it [Leo]. I went to school in the public schools — your usual thing. My elementary school was Hazeldell. Then my junior high school was Patrick Henry, and I transferred from Patrick Henry Junior-High School in Cleveland to Roosevelt Junior High School in Cleveland Heights. I got there either by walking from University Heights or taking the bus. That's where I first met Lois, because she was a good friend of my cousin Judy.

I was a good student, but I had terrible handwriting, and it's only gotten worse, to the point that when I was maybe 10 or 11 years old, the teachers got together and decided they would refuse to correct my homework unless it was typed, so I learned to type. So I'm a pretty good typist. I used to wear white shirts to school — in junior high school — white shirts and a tie. It was white shirts because I could never make up my mind — if I had colored shirts — which shirt I should wear today. So white shirt was always the easiest, so when I went to IBM, which was a white-shirt place, it was very natural for me.

Then of course in 1941 — Pearl Harbor. War broke out. I was in high school, Cleveland Heights High School. The program was accelerated, so I finished high school — I had skipped a grade, or maybe a grade twice, so I graduated in April 1944, as I recall, and went to Case. I had applied to several schools, including University of Chicago, and several others. I got a full scholarship to Allegany College, but it wasn't much of a college, so I didn't consider going there — and a scholarship to Chicago, and I think only a half-scholarship to Case, but I could live at home, so I did — and graduated there in 1947, probably April 1947, and began my graduate work at the University of Chicago in physics.

Ford:

As a child, when did you first start demonstrating technical capabilities, scientific capability, or scientific interest?

Garwin:

I was always interested in how things worked, so I would take things apart. Before I could talk, I would take things apart. For instance, my mother used to tell the story that the doctor was examining me as an infant, and I took apart his stethoscope — not to mention plugging the aluminum plug from a hot water bottle into the screw-type output that they had in baseboards in the old houses — and a number of things like that. You know, it was really very interesting. You would make string telephones with cans and think about those things. There were the dictionary, and the encyclopedia, and all these handbooks, so I remember reading up on fuel cells from a book which was published in 1917, I think it was — Chemical Engineeer’s Handbook. Or maybe it was the Mechanical Engineer's Handbook — and all these wonderful things.

Then we built the darkroom. We had a darkroom in the house on Paxton and again in the house on Washington Boulevard. The house on Paxton was right next to the coal bin, because that house had a coal-fired furnace. A truck would come with a chute and deliver coal through the trapdoor, which was a window, into the coal bin, and then you would shovel the coal into the furnace. After a while, we got a little stoker, so you could put the coal into the hopper, and the stoker would then carry it the rest of the way into the furnace together with a thermostat. All those things were very interesting. You'd find out how they work. I have some of my high-school papers on vacuum pumps or whatever.

Then when dad was in business, I helped him and troubleshot amplifiers, made some amplifiers, devised some new things myself, understood these things. I was interested in glassblowing, not for artistic purposes, but it's something that you can really make things, useful things — distilling stills and things like that. So we got some burners and some marble plates from old toilet stalls or whatever, so they would be fireproof. Then the shop that dad had behind the garage, where he had the Garwin Theater Equipment Corporation — GARTEC — there was a lathe, not with automatic feed, but when I was in high school I took shop, so I learned how to run metalworking equipment – and again at Case, and engineering drawing. So those were all useful tools. So from the time I began I was interested in technical things.

When I graduated from Case, my mathematics and astronomy teacher — McCloskey — urged me to get a degree in mathematics, and he was very disappointed when I decided to go into physics.

My father was disappointed because he thought I should go into engineering, because physicists just had theories and it was the engineers that did things with their hands. In fact, in the modern era, engineers design things with theories and tables and whatnot, and they don't know what to do with a physical thing when they're presented with it. So my kind of physics is much more hands on than the engineering that my dad thought I should do.

Ford:

You and your father, did you have great discussions about your career and what you were doing?

Garwin:

No, we didn't have discussions about career, or most anything. We were just — we would work together if there was something to do, whether it was fixing the car or an amplifier or whatever, and we would talk about that. We didn't talk much about philosophy or career plans, so I was just left to myself to decide these things.

Ford:

You wrote in a note to me something to the effect that your parents had told you not to compete with other people, because you had unfair advantages?

Garwin:

Yeah, I was too smart.

Ford:

Did your father talk to you about your personality? What type of fatherly advice, if any…?

Garwin:

I didn't get much fatherly advice. They led by example. They were not intellectuals. In fact, after I'd gotten my degree and was at the University of Chicago for five years altogether — including my graduate work and the time on the faculty, two years, two-and-a-half years on the faculty as an instructor and assistant professor — then I joined IBM at the IBM Watson Scientific Laboratory at Columbia University, and that was first at 612 West 116th Street. When I was there, they were building a new place — converting an old place — at 612 West 115th Street, so they ran both of those buildings for a while, with the West 116th Street activity really an instructional enterprise in computing for the Columbia community. Our laboratories were at 115th Street.

I had an adjunct appointment on the physics faculty at Columbia, and used to have lunch every day in the faculty club at a set table of physics, mathematics, and astronomy people — 8 or 10 people. Some of these people were very proud of being intellectuals, like Polykarp Kusch or even I.I. Rabi. But I wasn't an intellectual, I told them. Didn't like to be an intellectual. I just did what I could.

Ford:

In high school and college, did you do much studying beyond science?

Garwin:

I took the regular courses. Yeah, I studied history in high school. I had started French when I was in kindergarten, because in Cleveland they had a person — Emile Desauzé — who had created language instruction not only in French, but other languages. It was 15 minutes a day or so in some language or other. I was French during my whole elementary school activity. Then I took French and German in high school. Studied history the way everybody else does. Social studies. Standard courses. But I wasn't interested in history. Didn't like to learn dates. They're not related to a whole lot of things. Of course, that's wrong. If you're really a history bug, then you have as many relations there as you have in science, but I specialized. I didn't have very many friends. A few friends. Didn't play sports.

Ford:

Who were your closest friends?

Garwin:

I don't know that I had any really close friends. I had a cousin who was the nephew of one of my uncles — that's a man who married my Aunt Margie. So, this person was named [something] Goldfarb. We had a lot in common, so we saw one another maybe a dozen times or so. I didn't have a lot of friends.

Ford:

Did you have any particular hobbies?

Garwin:

My hobby was studying, glassblowing. I swam. My family had a cottage some of the time in a small place east of Cleveland — and photography, I guess.

Ford:

Did you ever keep any type of journal?

Garwin:

No. [Later on] I did have notebooks — that is, notebooks for putting physical ideas or recording work experiments. For a while I kept those pretty religiously, so there would be a sequential record of whatever I did, but it wasn't every day. It was just whenever I did anything. But I don't have a journal.

Ford:

Do you still have those?

Garwin:

Yes. They have some inventions, for instance. I invented something that's really very useful for optics and for electronics. It's called an isolator — a Faraday rotator. It turns out that almost everything you do is reversible, so if I can see you, you can see me. So I was in college and had a laboratory class measuring the rotation of the plane of polarization by sugar or by other molecules. So you have vertically polarized light that would go through a polarizing filter, like Polaroid glasses, and if you put it through water, it's still vertically polarized. But if you put it through sugar solution, then it gets rotated to the right or to the left. There's dextrose, which rotates to the right, and there's levulose, which rotates to the left. Otherwise they're identical compounds. So that's fascinating. Pasteur discovered such things.

Then in physics there's another rotation of polarization. If you put glass in the path, glass doesn't rotate the plane of polarization of rotation at all — unless it's strained, which is another story. But if you put the glass or anything else in a magnetic field along the direction of the light, then the plane of polarization gets rotated. But if you send the light back, the rotation is added for the magnetic field, whereas it's reversed for the sugar solutions. So, it rotates to the right this way, and you send it back; it rotates to its right, so it comes back exactly where it was. But with the magnetic field, the Faraday rotation rotates to the right in going through, and if you send it back, it rotates more — so it's going to the left. So I said, "Well, if I combine that with a direct path, then I can have a one-way transmission. I can have light, which goes in one end and comes out the other undiminished, but light coming in the other end doesn't come through at all." So this is the Faraday isolator, which turns out to be very useful.

Ford:

When did you do this?

Garwin:

When I was a sophomore, I think, in college — so probably 1945. I haven't really looked to see the classical — who invented the Faraday isolator — but it'd be interesting to do.

Ford:

You just sort of invented it by yourself?

Garwin:

Yeah.

Ford:

But it was something that was already…?

Garwin:

I don't know that.

Ford:

You don't know?

Garwin:

I didn't hear about it until a couple of years later, but I don't know where it came from. I could look it up.

Ford:

But somebody else invented —

Garwin:

Oh yes. Yes, that's right.

Ford:

What type of thing is it useful for?

Garwin:

Laser systems, so that when you have a laser that produces output power, any reflections beyond that don't come back and injure the laser. In microwave systems, so that power which is generated by the klystron or whatever goes out the antenna port, and power coming in through the antenna goes another way; it doesn't come back to the power source. Although for that purpose, you can use a circulator, which is not an isolator. It's a different sort of thing.

Anyhow, I went to high school. Of course, I was in high school on Pearl Harbor Day. I remember that — then to college, and that was accelerated, as I indicated. Then of course the war was over when I was in college, a year after I started. Then I finished my bachelor’s degree, went to the University of Chicago. And University of Chicago, because this nuclear physics from the atomic bomb seemed to be a good thing to learn about — and I wasn't particularly passionate about learning anything specific. I just wanted to learn more, so I went there. Fermi was there, and a whole stellar cast of faculty. I took courses, and after a few months of courses, I didn't have anything to do with my hands, so as I mentioned, I went to Fermi and I told him I was pretty good in the laboratory, and if he had anything he was doing that needed help, I would be glad to help him. So he did, and I did.

Ford:

In college, was there any particular professor or teacher who was highly influential in terms of —

Garwin:

There was one who was pretty close to me — Robert Shankland — but he died. He took an interest in me, and he had been at the University of Chicago. He worked with Arthur H. Compton. So I suppose that he urged me to go to Chicago.

Ford:

In terms of teaching you the tricks of the trade, was there any particular trick or approach or philosophy to scientific work that someone opened your eyes to?

Garwin:

In college you have laboratory courses, for instance. These are set pieces, and you measure the thermal expansion of liquids by having the specialized bottles, and you weigh the liquid when the bottle is full. It's arranged with a ground glass stopper in a tiny aperture. Then you wipe it off, and you heat it up, and you take off the excess liquid, and you weigh it again. In this weighing, you learn the tricks of the trade. You learn you should weigh it one way, then you should weigh it the other way, and if the answers are different, you have to explain. Ultimately, if there's no reason for the difference and it's small, you average. And you time things. Time things by precision clocks, pendulum clocks, for instance — and they had several such precision pendulum clocks.

Then you realize, when looking at these things, the rigidity of the support on which — the knife edge on which the clock is supported affects the period, the rate at which it swings. So you have to do something about that. Sometimes you have two pendulums on the same support, so that the knife edge doesn't move at all, because when one is accelerating this way, the other is accelerating that way. So there are a lot of tricks.

Then you say, "Well, I can do it better." So they had a chronograph for measuring the speed of bullets, or a ballistic pendulum. You weigh the bullet, and you fire it. It goes into this pendulum. The momentum is conserved, so the same amount of momentum in the bullet as there is in the bullet-plus-pendulum after it strikes, and then the pendulum goes to a certain arc angle, and you calculate what momentum it had to have to do that. I figured, if the job was to measure the speed of the bullet, there's a better way to do it. I just put up a few pieces of paper — cardboard — with thin copper wires across, and the bullet came through the first one and it broke a circuit, a capacitor, that stores electrical charge — was being shorted by that copper wire. When the bullet came through that, opened that switch, then current from a battery through a resistor would go into the capacitor and start charging it — maybe a volt per millisecond or something like that. Then when the bullet struck the second copper wire, that was in the charging path, and now the capacitor was isolated, and you'd had all the time in the world to measure the voltage on it.

So you would do that, and you could just calculate everything. You didn't have to have the pendulum. You didn't have to have… So I did it both ways, and that was pretty nice. Then there was something else — I still have the records from it. It had to do with the pendulum. I made a camera. We had movie film around the house, and sprockets, and so on. So I would record these things for a long time.

You try to think how to do things better, and you do them. I learned very early that — at least, I didn't have any confidence in the theoretical approach of solving these problems, because I could make too many mistakes. So I would try to understand it one way and calculate that, and then try to understand it another way and calculate it this different way, and if they didn't agree — which was a red flag — I knew that at least one of the ways was wrong. So I did that for many years, and it's still a good thing to do. It avoids being prejudiced, [it avoids] being so sure that you're right and that there's only one way to do a job.

When I joined Fermi, he was a master experimenter, as well as a master theoretician. His courses were models of clarity, and he was very good at asking questions — what is it that was important to measure to advance our understanding. I don't have that passion or talent. My strength is in actually doing something, when I think that would be a useful thing to do. It's not so much in asking the important physical questions. Fermi had invented the theory of beta decay to account for the natural, long-time radioactive decay of naturally occurring materials. He did that in 1931 or '32. Then he changed entirely to experimental work in his group at the University of Rome — and discovered the effectiveness of slow neutrons in producing artificial radioactivity, and understood that thoroughly.

They looked at uranium, and they found all of the strange activities that were produced in uranium. For four years, they and the entire physics world absolutely missed the obvious solution that the uranium nucleus was breaking up into many different pairwise combinations of radioactive materials. Only Ida Noddack, a German chemist, had proposed this solution and even visited Rome and told the people there, but they rejected this idea because she didn't know enough physics. It was just not the way nuclei behaved. No, you might get a neutron off, or two neutrons, or a proton, but the idea — and you could show it very difficult for a nucleus to break up into two big pieces — until the experiments were irrefutable that one of these [radio] activities behaved just like barium, chemically.

Ford:

Who was the woman who —

Garwin:

Noddack, who was a German chemist.

Ford:

I've never heard of her.

Garwin:

It's in my book a little bit, but told better elsewhere.

[off-topic]

Ford:

Tell me more about what your fundamental skill is. You said it's not asking questions about physical principles?

Garwin:

I'm best at looking at a problem either that I want to solve for some reason or that somebody else has, and understanding where they are, and being able to take a next step — sometimes a big step. Not necessarily solving the entire problem, but just doing something useful.

Ford:

But you had to have had quite a full training in the principles of things to begin with.

Garwin:

Oh yes. When you look at something, you have to understand what's going on and immediately have an idea of what theoretical approaches are relevant, what computational approaches, the whole panoply of things that you could do to the system in order to change it in the way you would like it to change. What's really necessary, or else other people would've solved the problem before, is sometimes you need to have two novelties, two simultaneous advances, in order to take the next step, because it's pretty easy to look around in a toolbox and see which particular tool could do something useful — but if it's two tools used simultaneously in a different way, that can make a big difference, and it's much harder to think of.

We did that, for instance, in our experiment that I did with Leon Lederman and Marcel Weinrich in January 1957 to show that the universe and its mirror image would not develop in the same way. This was the pi meson, the mu meson, and the decay, and to the electrons. So our friends T.D. Lee and C.N. Yang had written a paper in August of 1956 about this possibility and the likelihood that, very unexpectedly to everybody, there would be very big differences between the decay of a mu meson and its counterpart — or for that matter, that mu meson, which has a spin one-half and which, up to that time, everybody thought would decay isotropically — that is, same number of decay electrons in each direction. [We found that if] you polarized it — that is, oriented the spins all the same way — it would not. This was really revolutionary and has, as the consequence, that the mirror image, or the charge-reverse system, would not behave in the same way at all.

So they [Lee and Yang] proposed that radioactive materials like cobalt-60 — five-year half-life, a very common radioactive material — if you could orient the nuclei all pointing in the same direction, then the electrons might come out more along or opposing the spin than the other way around. Another of friend of mine, Chien-Shiung Wu, Professor of Physics at Columbia, was an expert in measurement of radioactivity, and she wanted to do that experiment. She knew I was working in low-temperature physics, so she asked me whether we could do that together. That was probably in August 1956. I told her no, that I had just started a superconducting computer project at IBM and I was in charge of 100 people, and I really couldn't do that, and that what she ought to do was to talk with the people at the Bureau of Standards. So she did, and they ultimately did that experiment together.

The other experiment that Lee and Yang had suggested was that somehow you look at the decay chain of pi mesons that are made by high-energy collisions of protons with nuclei, or protons with protons. These pi mesons only live for about 20 nanoseconds. They decay into mu mesons, muons, that live for about two microseconds, and the muons decay into an electron and two neutrinos in this two microseconds. They said that, if you followed the progression from the pi meson, which does have to decay uniformly in all directions — but you take one of the mu mesons that's created. It goes off in a certain direction. Then the electron that follows from that decay is more likely to be in the same direction of the muon or opposite — but they didn't know. Anyhow, not uniformly in all directions compared with the muon direction, or speed, or velocity.

Many people started doing such experiments, but the mu meson only goes about eight-tenths of a millimeter in photographic emulsion before it stops. So people would look at the track that the mu meson would leave in the photographic emulsion, and the track that the electron following would leave. So you capture thousands of pi mesons in this photographic emulsion — positive pions. They decay before you can take the film out. Then you have developed film ultimately with these tracks in it. Then you hire a lot of scanners to look at them and to tell you which direction the electrons are going compared with the muons for each of these decays. But it's all too easy for the muons simply to scatter a little bit and look like a decay electron, so people were getting all kinds of answers — yes and no.

Finally Leon Lederman and I had these two ideas. Leon said to me over the telephone — I was just coming home from my superconducting computer program activity in Poughkeepsie on Friday night. He called me up probably around seven o'clock or so and said, "You know, I've been thinking. Maybe these muons that we've been stopping outside the cyclotron for years are all polarized because they are formed from the decay of the pions in flight, and we preferentially select the muons that are going forward. So you don't have to look at a particular pi meson decaying to a particular mu meson decaying to its electron. This whole sample of mu mesons may be all spinning in the same direction, and when we stop them, we would just have to make sure that we don't depolarize them, and then we have to get a counter that will swing around the sample and see whether there are more electrons in one direction than the other."

Why'd he tell me instead of wanting to do it himself? Well, because he thought it would be done better if we worked on it together. So I met him at the cyclotron after dinner, an hour and a half later. The cyclotron was going to shut off Saturday morning for its weekend maintenance and turn on Monday morning, typically. But there was more maintenance to do this time than usual, so it wouldn't start going until Monday evening.

We looked around to see whether there was a counter that we could move to different positions. We know about such things but didn't have any, right there. Then I said, "Well, we don't really need to do that. In fact, it's better if we don't do that, because when you stop the mu mesons there in a block of carbon — graphite or whatever, metal… Some of them will be near the front face and some the back face, so if you count the electrons that are coming out the back, and then you would move your counter to count the electrons that are coming out the side, the electrons have to go through different distances of this absorbing material. So in addition to the effect you're looking for, if it's there, then there are these dirt effects of where the muons happen to stop in the target.

I said, "Wouldn't it be better if we could rotate the muons so that they were originally pointing in this direction, maybe. So let's just put a magnetic field on them so before they decay they'll precess to their pointing in this direction — or a stronger field, this direction." So we could have a fixed counter and see how the count rate varies as a function of magnetic field, and we would get about, I think, 40 counts per minute or so. All we needed to do now was to wind a coil. There's another complication. We were about 300 feet away from the experimental apparatus because there's radiation in the room where the muon beam is, so we wanted something that we could adjust from where we were. Nothing is simpler than changing the current in a wire that goes to a coil, so I found a lathe. I found a plexiglass, Lucite cylinder. Found some wire, wound this on it. Figured how much wire, what kind of power supply. So we were running in two hours or so, and by Saturday morning around 6:00 A.M., we had a very big effect.

Ford:

You worked through the night?

Garwin:

Oh yes. Well, sure. So a very big effect, but by the time the cyclotron shut off at eight o'clock, the effect had vanished, and that was sort of distressing. It was not reproducible. We went down to turn off the counters, high voltages, and things, and we found that, because I hadn't glued the wire to the plexiglass, when I put current in the wire, it expanded and had fallen down at some point. So presumably the early data we had taken was correct, and the later data, there wasn't any magnetic field. So we spent the weekend looking for a counter that we could move around. Fortunately we didn't find anything, so this time I just wound the wire on the graphite block itself, which is a much better thing to do in the first place, and turned on Monday night. By 4:00 A.M. Tuesday morning, Leon had gone home. I called him up, woke him, and told him that we had this enormous effect just as — and by then I had worked out the theory and drawn the picture and written the [first draft of the] paper that was published in the Physical Review Letters, February 15, along with the Bureau of Standards experiment on cobalt-60 by Ms. Wu, and Eric Ambler, and others.

Ford:

That cyclotron was where?

Garwin:

At Columbia — at the Nevis Laboratory of Columbia University, which is in Irvington on Hudson. Nice place. The point there is that this advance took two ideas, and I didn't have them both. But the two of us working together had them both. One was that the muons were already polarized, and the other that you rotate their spins rather than looking in detail at the direction of the emission of the electrons. That's a little complicated to understand. The more theory you know, the harder it is to understand. I remember when I talked about it in Switzerland to [Wolfgang] Pauli and at Yale to Gregory Breit, both of them very good theoretical physicists. They were not willing to believe right off that you could just think about this classically, that each of the muons has an uncertainty as to direction, and who knows what the direction the electron's going to come off? But when you take the average over the whole population, then it's really a classical effect. The reason that I knew all this was that I had been working at IBM in nuclear magnetic resonance in helium-3, which is a spin one-half system, so it was really easy for me to do this.

Ford:

As a lay person, the significance of all this goes over my head.

Garwin:

Oh, we have a press release from 1957 that was very carefully constructed and printed in the New York Times. It really meant that world wasn't at all the way we had thought. It's like a Big Bang: Here you are in this universe that doesn't change with time, and so it's not obvious that, 15 billion years ago, it was totally different, that there was nothing until there was the Big Bang and all this started. Even on a lesser scale there are the ice ages, there is the fossil record. In the 19th century, people didn't understand that these fossils were millions of years old and not just produced a few years before in some way or another.

Ford:

Let's go back a bit to Fermi.

Garwin:

Fermi was a marvelous experimenter and theorist. I mentioned his contributions to theory and then his deft work with the slow neutrons, marred only by the missing of the discovery of fission, even though they had caused fission and measured its effects. By then, he had just come to the United States in January of 1939. And Bohr came on the boat and talked to people in Princeton and then told — then the word got to Fermi about fission. Szilard was a hanger-on at Columbia. Fermi had a professorship of physics at the faculty. Szilard, in 1932, immediately upon the discovery of the neutron, conceived of a chain reaction, that a neutron might liberate two neutrons somehow from some material, some nucleus, and those two neutrons — four neutrons. So you would have enormous multiplication of neutrons.

In fact, he got a small grant from the British government to do experiments, but he started at the light end of the periodic table, so he had no chance of getting to uranium before the money ran out. When fission was discovered, Szilard immediately recognized that this was likely to be what he had been looking for. He wanted Fermi, with the discovery of fission, to look at the chain reaction. Szilard had also realized immediately in 1932 that you could make powerful explosives with nuclear energy this way, if you could have a chain reaction.

[In January 1939] with the clouds of war thickening, and I guess war having started in Europe, the… Szilard was pushing Fermi actually to work on the chain reaction, and Fermi's inclination was to go back and study the physics of fission. Without Szilard's push, Fermi probably would've done that. So Szilard is likely responsible for the initial progress on chain reactions in this country. He had trained as a chemical engineer too, so Fermi worked on… Szilard was a very ingenious person, and they understood, as soon as they had thought about it a little bit, that the uranium-235 — which had been demonstrated very soon to be the fissile isotope — was only seven-tenths percent abundant in natural uranium, and that required very special configuration for a chain reaction to happen with the slow neutrons that were so effective in causing fission in uranium-235.

Slow neutrons are much more effective than fast neutrons, simply because they stay around longer and so they take longer to pass through the nucleus. They have a greater chance of causing fission. It isn't their energy that does it. The energy that causes the fission is provided by the capture of the slow neutron, which gives you about 8 million volts of energy, and that's enough to set the nucleus into vibration. So it has a chance of breaking into two before that neutron gets out, or before a lot of the energy is lost by the emission of gamma rays.

To make a long story short, they realized that you needed to have the neutrons born[??] in uranium-235, get out, spend much of their time slowing down in light material like water or pure graphite or oxygen, and only then diffuse back into the uranium. So that was the idea of the lumps of uranium in a moderator. They soon found that water wouldn't do as a moderator for natural uranium because the hydrogen has too big an appetite for neutrons. So heavy water would do.

This work was all shared between the British and the Americans, ultimately. The British then bombed the Norwegian plants — heavy water plants — to keep the Germans from getting the heavy water. The Germans had initially tried graphite as a moderator, but it absorbed too many neutrons and they gave it up. But Szilard knew that the graphite manufacture — heating oil, wood, whatever to very high temperature — was usually done using boron carbide electrodes or other materials. The boron has a tremendous appetite for neutrons, so tiny traces of boron in the graphite were responsible for this parasitic loss of neutrons.

Szilard then worked with the suppliers, got somebody to provide very pure graphite without boron, and that's how our first reactors were made: the Fermi Reactor that went critical December 2nd, 1942 in Chicago, and then the production reactors. Fermi’s Reactor was about two watts of thermal power maximum under the west stands, because it didn't have any shielding and would have exposed people to too much radiation. The next step was the design of these 200-megawatt reactors for producing plutonium. You get about one gram of plutonium per day for a one-megawatt reactor. So, 200-megawatt reactor, two-tenths of a kilogram per day, and the first Nagasaki bomb used six kilograms of plutonium. So you could make — every 30 days you could make a new core for such a bomb.

Ford:

Did you ever see the reactor in Chicago?

Garwin:

By the time I got to Chicago in April 1947, the graphite reactor had been moved to the Argonne laboratory. I worked on the reactor at Argonne just to make some of the radioactive materials for my thesis, but that was a heavy water reactor. The graphite reactor from west stands was CP-1 — carbon pile number one [it stood for Chicago Pile-1] — and the heavy water reactor was CP-3, which makes you wonder whether 'C' was really carbon. But it was CP-3.

Ford:

When you started working with Fermi Laboratory, we discussed before how you — one of the things you said was improved – some measuring device?

Garwin:

Yeah, well, Fermi was working with Leona Marshall, who had been with him at Los Alamos. She was a very energetic woman, and they were doing an experiment on positronium. So, you have radioactive materials, most of which emit ordinary electrons, but some of them — and almost all the emitters from fission are ordinary electrons, because uranium has a lot more neutrons per proton than do the lighter elements. So when you break up a uranium-[atomic number] 92 [atomic mass] 238 into half-sized things, they're [atomic number] 46, [atomic mass] 119. It's not symmetrical fission, but that's the sort of thing…

That's a lot more neutrons than those stable elements have, and these neutrons give off an electron in order to convert themselves into a proton. That's why all of the fission products are ordinary, negative-electron emitters. But if you make sodium-22, for instance, sodium-22 is a positron emitter. It gives off a positron in going to a stable isotope. The positrons, you don't see any positrons around here, do you? The reason you don't is that when they slow down, then they capture an electron of precisely the same mass, and they end up giving off two gamma rays of 511,000 volts each going off, incidentally, in precisely opposite directions.

If you think about it a bit, as people did, each of these electrons — positive and negative — has a spin one-half, and so you can put them together either with zero spin, ultimately — the two halves are opposite — or with the spin one, if they're in the same direction. Spin one-half can annihilate into these gamma rays, but the spin one has a lot of trouble doing that. It takes it much longer. So they were interested in determining the lifetime of these two different states: the parallel spin and the anti-parallel spin states.

Fermi, being a great experimenter, ordered from the marvelous Chicago University shop left over from the war effort — the metallurgical laboratory had been there — Geiger counters with little glass tubes attached. In this little glass tube, before they sealed the Geiger counter and filled it with the gasses that would convert the Geiger counter — well, that would allow it, when you put voltage on its center wire, to make a discharge when a particle passed though, which is what a Geiger counter was in the 1930s. You would put a little string, a cotton string soaked with a tiny amount of sodium-22, [parallel to the center wire]. Positrons would be born occasionally, and they would stop in the material of the gas, and then you would determine the distribution time.

Well, they could measure microsecond times, but they couldn't measure the nanosecond times that were expected from the spin-zero positronium. So I got to work. I told them that I could probably do something to help. I looked at how people measured these time differences, or got a pulse and compared it in time to another pulse. People used what are called coincidence circuits. The idea of a coincidence circuit is that it gives you an output when two pulses come in at the same time and gives you no output when they're displaced by more than a little bit from one another.

The Rossi coincidence circuit that had been known from the 1930s had typically a so-called resolving time — between calling it coincidences and calling it not — of a microsecond, a millionth of a second or so. That worked just the way my bullet-timing thing did. When one pulse came in, it opened the charging circuits. If something started going up and the other pulse came in — and it stopped the going up. So you were looking at the voltage on this capacitor. That's not exactly right. When one pulse came in, it started going up at a certain rate. When two pulses came in, it started going up at a considerably higher rate. But if you let it go up for one pulse long enough, than you would get to the same level as two pulses for a short time. So it wasn't a very good coincidence circuit. Thousands of people had used it. It was still a microsecond circuit.

I said, "The problem with that is that you allow the voltage to rise." That's because people were using vacuum tubes, and that's all we had. You can still use vacuum tubes, but there were semiconductor diodes available — not amplifiers, not transistors in those days — and if you would have the current supplied through a diode, then the difference between having all of the current — 20 milliamperes — and 10 milliamperes through that diode, it was only about half a volt, whereas the normal change of voltage in the Rossi circuit was 100 volts. All you really needed to do was to arrange that one input pulse, change the input current from 20 volts to 10 volts, and the other one — changed it from 20 milliamperes to 10 milliamperes. The other one changed it from 10 milliamperes down to zero. Then the current would no longer be coming through the diode, and it would start rising just like a Rossi circuit. So the discriminator, the next stage, wouldn't have to tell the difference between a rise of 15 volts and a rise of 30 volts. It would have to tell the difference between a rise of half a volt and a rise of a few volts. And that you could have climb to that level within a few billionths of a second.

I tried it, and I found a lot of diodes that didn't work because they had “stored charge,” things that diode makers didn't care anything about — but some that did, and they were reproducible. So we made a whole slew of these [coincidence circuits] for Chicago, for my work. I published it, and everybody used those for many years. Having made a two-input coincidence circuit, people would like to have coincidence/anti-coincidence analyzers so that you have a whole lot of things. Cosmic rays have particles coming in. You would like to have a real output only when it was not due to a cosmic ray. There were no cosmic rays coming in, but just some radioactive decay happened, or particles went through this counter and not that counter.

So I made a 10-input coincidence/anti-coincidence analyzer that would have six vetoes. If a pulse showed up in any of those channels, it would null the coincidence output. Then on the four coincidence channels, you would have three particular choices: You could have a four-fold, two-fold, three-fold, whatever. In an experiment, your counters would come into this front panel, and there would be three outputs, and those three outputs could be arranged to be a particle that went through this counter, and that counter, and that counter, but stopped there. Then another output, a particle went through that and the next counter, then stopped there. Anyhow, a very useful thing. I made a couple of those and used one in my work at Chicago.

When I was leaving a year or so later to go to IBM, even though I didn't expect to be in this field at all — you never know — I had IBM buy one of these made by the University of Chicago electronics shop, and I gave it to the people at the Nevis cyclotron so they could be using it. Why should it sit on my shelf in my office? So [four years later] in 1957, when Leon and I had this idea, we just pushed his graduate student aside — Marcel Weinrich — who had been counting these muons in these beams and had had a problem getting his thesis done because, for some materials, the decay of the muon was not exponential, which it has to be. Any radioactive material has a half-life, and half of it decays at a certain time. Then, no matter what went before, half of that decays in the same time. So it's exponential. But his were not exponential. If you plot the logarithm versus time, it should be a straight line. He had wiggles, so he was trying to understand that.

Of course, what was happening was that he was seeing the very world-shaking event effect that we were looking for, but in the uncontrolled fringing field of a cyclotron, you have this big thing — 15-feet in diameter with a magnetic field 10,000 times the strength of the Earth's field, and it falls off outside the gap, which is big enough to crawl into. I've done that many times — and in the counting room it's still bigger than the Earth's field, and so you shield your counters from that because they won't work if you don't shield them. But who thought of shielding carbon blocks in which million-volt particles were going? What happens is that that muons, when they stop, continue to spin in this external field, so our discovery was what was keeping him from getting his thesis because it was contaminating his result.

[Returning to your question as to how I got started,] Fermi was doing that experiment, and I started helping him by building these coincidence circuits. To do that, I had to make fast pulsers and create a whole little field. Then he also was thinking about shell structure, as the people had been working hard on nuclear physics.

Ford:

Are there photographs of things like the coincidence circuit?

Garwin:

Yeah, I have a couple. I think I have my coincidence/anti-coincidence… I have my Schrodinger differential analyzer. So he wanted to actually do some computations, numerical computations, of the behavior of the nuclear particles, protons and neutrons, within the nucleus. He had the idea that, just as we have atomic shells for electrons, that in the nucleus, the successive protons and neutrons could organize themselves into these shells. They're determined by the radiowave function and by the angular momentum. That's absolutely fundamental in physics.

He wanted to do some calculations, and he said that he would support a magnet in a horizontal magnetic field — just made by winding a wire around a cylinder — and that if he would then change the current through that magnetic with time the way the potential, the energy, of the proton or neutron in the nucleus varies with space, then the swinging of the magnet would mimic the wave function of the neutron or the proton.

Sure it would. It was perfectly clear. But you would still need a way of recording this just the way I had recorded from — and people had done for many years — from a mirror attached to the magnet. I said, "Well, there's probably a better way. What you're doing is simply to calculate this differential equation so let’s use electronics rather than swinging masses. We'll have a voltage here, we'll have an amplifier. Two of these amplifiers connected in series with some capacitors would do this — would mimic this differential equation, and all we need to do is to change the coupling" — that is, you have a volume control, essentially, and there were such things available in a linear range…

You would have a piece of paper, which is carried by this sprocket, and the experimenter would then follow the line on the piece of paper, which was typical of the potential — that is, the energy. Then another output, another strip-chart recorder, would then draw the wave function. That's exactly what you want to do. He said, "Yeah, that's a better thing, so build it." So I built it, published it. A rather complicated thing. Of course, by '54 or so, when Fermi died — he used it some, but when he died, digital computers had come along, and it was a lot easier to use digital computers than to continue to use this thing.

Ford:

Was that your first scientific [???]?

Garwin:

No. I think my first was some things I had done in relation to my bachelor’s thesis at Case. I had made little toy homopolar generators — that is, spinning discs, flywheels, that would produce very big pulses of energy. The idea was to use these for power and particle accelerators, so I made some of those, and I also made an analog computing device for determining the shape of coils to produce specific magnetic field shapes.

When you make such a disc — about six inches in diameter… I made of beryllium copper, and I milled little air nozzles on the edge, so this was driven up — spun up — by compressed air rather than by a motor attached. Then you say, "What's the limit? How fast can this thing be spun?" Well, it breaks because of centrifugal force if you spin it too fast. Everybody knows that. But if you would stop it too quickly — we could stop it in half a revolution without adding really much to the stress from centrifugal force, because that reverses the direction twice a revolution.

If I had a whole stack of 200 of these discs — half of them going one way, half of them going the other way — then the voltage created in one of them would be positive going out, and in the next would be positive going in. So, a serpentine path down this stack would add all these low voltages. You'd get high voltage instead of this very low voltage. So I think I published that first. Then there were my pulse things, and then after that the… Oh, then there was an improvement in counters.

At Chicago, Fermi, and Marshall, and Jack Steinberger — who later got a Nobel Prize… He was doing a thesis with a stack of brass Geiger counters on cosmic rays with graphite, looking at the lifetime of muons, I guess — which wasn't very well known at that time. As we were getting ready for work with the cyclotron, we had the experience of the Berkeley cyclotron, we were building a 450-million volts, half-billion volt cyclotron at Chicago. As a training machine, we had from General Electric a 100-MeV electron machine, a so-called betatron.

The characteristic of these machines is that you can get external beams from them, so the protons come out or the pi mesons come out, and then you can scatter them or absorb them or whatever, and that's the meat of physics experimentation and theory. But you like to define the beam — that is, to count the particle without disturbing it very much. That means it has to go through a small amount of material. Then it has to go on. You want to have fast counters so that you could have a high particle rate. A lot of them per second without having an accidental coincidence — that is, a count here from one particle being said to cause a count here in another counter, when in fact it was two different particles that did it.

So you can see, as you increase the rate, then the number of accidentals goes up for a two-counter experiment — like the square of the rate — and the number of reals goes up only linearly with the rate, if one does what you wanted. So there's a limit to how fast you can go. If you're having four-fold coincidence, then the accidental rate goes up at the fourth power. So even though it helps you a lot, you still have a real problem with increasing rate. So the short coincidence resolving time is very important there. That's why my coincidence circuits were important.

The other thing that's important is to be able to have these thin counters and fast counters so the pulses themselves are fast. Well, people had used scintillation counters, so when a particle goes through sodium iodide or whatever, it produces a lot of light, and in seven-tenths of a microsecond, the light dies away. But organic scintillators — naphthalene, anthracene — naphthalene is moth balls — they scintillate too, so we were making scintillation counters. I grew anthracene and naphthalene crystals that big. I made my own furnace. I grew them, but they're fragile, and you can't get them in very big sizes. So people started using plastic scintillators built with fluorescent materials, and then some of the folks at Chicago experimented with liquid scintillators. These would be toluene, organic solvents like that – and with some naphthalene or other materials in them that would take the ultraviolet light that's produced by the native material, convert it to visible light right within the scintillator, and then you would capture that in a light pipe — you know, like a Lucite rod, glass rod, which you have illuminate one end then it goes a long way, comes out the other end. Or a sheet of glass, whatever.

I noticed this, and I said, "Well, let's take these light guides that have been made for crystals, and I'll put two very thin plastic sheets over them and a little hole for filling the liquid — put the liquid in." So I made some of those, and I tested them, and they worked very well. I published that after quantifying it. The other contribution was that people had tried to have big scintillation cells, and to get the light into a little photomultiplier…[???].