November 22, 2017 (PO61). John Stewart Alcorn was born on February 29, 1932, in Tulsa, Oklahoma. His family moved to Houston, Texas in 1935, where he grew up. He graduated from The Rice Institute (now Rice University) in 1955, with a Bachelor of Science degree in mechanical engineering. In the United States Navy Reserve, he was commissioned as Ensign.

As an engineer, he joined Aerojet General Nucleonics, San Ramon, from 1958 till 1961 and did transportation studies for laboratory scale, gas cooled, mobile reactors. From 1961 till 1965, he worked for William Brobeck & Associates in Oakland, designing electromagnets, dipoles, and quadrupoles for HEP research at the Rad Lab and at LLL. For the next 10 years, from 1965 till 1975, he was involved in the design, fabrication, and installation of the copper magnet for the 40-inch liquid hydrogen bubble chamber at the Stanford Linear Accelerator Center. In this context, he worked also on the design and fabrication of various copper beam handling magnets and the design, construction, installation, and testing of the Large Aperture Superconducting Solenoid, (LASS).

In 1975, he joined the General Atomic Company, San Diego, for the next 14 years, till 1989, working there on the design and construction of a number of superconducting magnets for high energy physics, power fusion research, superconducting magnetic energy storage and power grid leveling. From 1989 on he had the oversight on design, manufacturing, testing and installation of the large superconducting dipole and quadrupole magnets as the Hall A engineer in charge.

Later, he was consultant and advisor to LANL with respect to the reactivation of the LASS solenoid in the MEGA configuration, and also to Indiana University with respect to the reactivation of the LASS - MEGA solenoid within the framework of Hall D at JLab, where he also advised with the reconfiguration for the purposes of GLUEX.

A Personal Memoir.

Fall of 1964. A meeting took place in Building M1 at the Stanford University, then still known as the Farm, at which the need for someone to design and build a magnet for the planned hydrogen bubble chamber was recognized as essential. A young engineer, John Alcorn by name, was recruited a little later from the engineering pool at the fledgling Stanford Linear Accelerator Center, SLAC, and assigned to do just that in the nascent Hydrogen Bubble Chamber Group where I met him for the first time. John was magnets, I was cryogenics, different interests, yes, but somehow, we gravitated together. John professed to be a runner, I claimed to be a bicyclist, we both played tennis, we both loved to hike in the mountains of the Sierra Nevada. We both loved a good discussion, political or technical, which was not important. John was not a reticent character by any means but it took me quite some time before I found out that he was a highly talented artist who expressed the newsworthy events of the day in elaborate pencil compositions somewhat in the manner of Diego Rivera but on a much smaller scale and much more delicately. I also found that John had a fiery temper, just like that artist, offset by an impish sense of humor. He claimed that the reason for his manner was that he was born on the 29th of February and thus was deprived of three birthdays every four years! Not only was John an artist, he was a superb craftsman, a builder of solid models of aircraft, of aircraft of one kind: the fighter planes of the Battle of Britain time. As we were both students of that particular period, we had both opinions about the hardware on a daily basis. While we were building the bubble chamber, John found the time to make an absolutely fabulous scale model of the Spitfire, which is now in the Smithsonian. A decade or so later he produced Daisy Mae, the Douglas A-20 Havoc bomber, which also landed in the Smithsonian. (John is holding the model in the photograph)

The bubble chamber construction proceeded well and John and I began to mesh: I needed more space for my pipes, which he was loth to give as it “reduced the field”. The bubble chamber was commissioned successfully and began to participate in the physics program, John disappeared to make more copper magnets and I to explore this new phenomenon of high field superconductivity. As the 12 foot superconducting magnet for its bubble chamber had just been completed at the Argonne National Laboratory, the confidence in superconductivity rose at SLAC with the result that a complex, multi-coil solenoidal spectrometer was planned. This brought John and me together again to design, build, test, and argue. The project, the Large Aperture Superconducting Solenoid, LASS, was and is a testament to John’s engineering talent. Apart from the field analysis, every component in that assembly of four separate solenoidal coils in iron shells was analyzed with a slide rule and meticulously documented. John guided the design, procurements, construction, the coil winding and insulation, with an eagle eye. When I recall now how limited the resources were at the time, everybody had at least two other obligations, I marvel that LASS was ever finished. But John willed it and it became the forefront of an extensive physics program.

During the construction of LASS, John was often in contact with John Purcell at ANL and established a well-knit collaboration at a distance. So, when LASS was completed and no further superconducting magnets were planned at SLAC, John decided to leave its fractious physicists, and defect to the calm of commerce, to the General Atomic Company in San Diego to be with JP as co-head of the new Superconducting Magnet Group. At that time G.A. was deeply involved in designing the PGFR, a power generating fusion reactor, with superconducting ‘D’ coils. In in the years following John participated in a number experimental programs such as the 10-tesla high field test facility, the 12-tesla model coil cooled with helium II and numerous studies and coil concepts toroidal field magnets for the Engineering Test Facility and fusion power research, GA’s primary mission. He was also involved in the design of the 30 MJ energy storage coil for the Bonneville Power Administration, a project he was particularly proud of and which had interesting consequences for both of us.

John was a unique individual endowed with the ability to make his friends and colleagues participate in his adventures in which common sense was not always immediately obvious. So, it came to pass that the fruits of the 1982 Applied Superconductivity Conference hung by a thread or more correctly on a few sheets of plastic. In Knoxville John divulged a secret to me: his great desire to find a 1956 Chevrolet hardtop coupe and he thought that in the hillbilly country around the town he might find one. Instead of attending the meeting he wandered around the countryside and indeed on the third day announced success. Would I help him get it home? Of course, I would as long as I could take the conference papers with me. I was the editor at the time, and I was not going to let the scientific effort of the past two years out of sight. Agreed, and all we had to do is to chase the resident chickens and get the black vehicle out of the mud. A day later the engine was sputtering, the wheels were turning shod with new tires, the trunk declared unusable and the precious boxes with manuscripts carefully wrapped in many sheets of plastic on the back seat. We visited a car wash but gave up when we noticed that the windows were leaking and the more we washed the weaker the insulation on the wiring became.

The departure from Knoxville was very slow, the supposedly moving parts of the car did so only reluctantly, but we had plenty of time. As the mud fell off our speed would increase in mini-quantum leaps, rather disconcerting, but by the time we reached Memphis we were moving quite nicely. I should mention that we were the sight of the day for the locals: a 1956 Chevy! At the Tennessee border, John declared that he needed to find the original hubcaps and so for the next few hours we cruised the junkyards in the states of Mississippi and Arkansas finding nothing. As we were crossing the Mississippi River, we ran into a tornado, at least we ran by it but could not escape the rain. The car leaked like a sieve. The manuscripts were safe but we were soaked to the skin. The hospitality of the folks in Little Rock fixed all that, after all, we drove a 1956 Chevy and her name was DoraBella as befitted a Southern Dame!

We made it to the Rockies, as we were about to cross, naturally, it started to snow and the temperature fell like a rock, no heat in the car. Imagine the comfort of that ride, but we made the West.  The papers were published, John and DoraBella disappeared in San Diego, to reappear some years later, DoraBella superbly restored in a red and cream livery, bearing the vanity plate ‘Rice 56’, John’s alma mater.

En route John displayed yet another one of his accomplishments: he recited Chaucer’s ‘Canterbury Tales’ of what we both fondly believed to be the Original English as she was spoken then. Heard once, super, heard twice, ok, heard three times, a walk home became preferable.

Thirteen years of commerce taught John the arcana of schedule and budget, an art not unknown but not necessarily practiced by the physics community so when he was invited to CEBAF he was well equipped to assume the role of Hall A engineer to create a pair of High-Resolution Spectrometers, each consisting of a superconducting dipole and three quadrupoles. His dipoles have an interesting design, the coils have a positive-negative winding profile and the limited cryostability of the superconductor owes much to the concept he pioneered in LASS.

A talented, experienced engineer as John always finds someone who needs help. And so, in his case also, even at a distance. On the West Coast, the fates decided to involve John again in local intrigues. LASS had ceased physics activities and was essentially abandoned but a group of physicists at Los Alamos National Laboratory decided that the solenoid would be suitable for their program. About this time, I learned that the Bonneville Power Administration’s energy storage project was winding down and with it the associated 1 kW helium refrigerator. While the need for such a machine at SLAC was not immediately obvious, an ‘exchange’ seemed opportune. LANL received LASS, SLAC a large refrigerator, and John became a participant once again. With his help and advice LASS became MEGA and more physics followed.

Some time at the beginning of this century I heard that MEGA had been retired, as a result of some inquiries from one Alex Dzierba of Indiana University who asked whether the magnet was operational and whether it could be transported to CEBAF, by now JLab, for experiments in the new Hall D. The interested parties, including John, met at Los Alamos, found a well maintained three coil MEGA and the fourth coil in the crate in which it left SLAC fifteen years ago, burried in the desert sand outside the laboratory fence. In due course, the magnet was shipped to Indiana and subjected to further indignities which led to numerous electrical and instrumentation problems. MEGA became GLUEX, the coils and iron were reconfigured as also was the cryogenics. Ultimately GLUEX, or at least its solenoid, became a working magnet once again.

It is a huge tribute to John’s engineering skills that so complex a device as the LASS solenoid quartet should, after more than forty years and countless miles of travel and major modifications become operational once more. As soon as I received the news, I attempted to inform and congratulate him. I was too late.

Steve St.Lorant, October 2017.