Commercial cryostats

It was ILL's initial policy to buy the cryostats commercially available [1]. The directors had seen or used them in the past and thought they would do the job. As we shall see, this was far from the case, and cryostat design made major progress thanks to the ILL.

(The sample is loaded from below)

Cryogenics Associates' CT14 cryostats (blue in colour). These came in from the USA and were widely used at Brookhaven in the early seventies. The sample was positioned in a sealed holder fixed to the bottom of the liquid helium reservoir. Thus, changing the sample implied successively draining the liquid helium, draining the liquid nitrogen, heating back the whole device to room temperature, opening the sealed holder and then performing the reserve operation. It took 6 hours to change the sample. This was acceptable for low-power reactors, where experiments could last weeks or even months, but it wasn't good enough for ILL. It's even truer today, as the pace has changed and ILL's instruments have gained by a factor of 25 in efficiency.

(Sample loaded from above)

TBT/Air Liquide cryostat (black). The sample stick can be seen at the centre of the photo, together with a very basic temperature control system.

Stoehr cryostats (stainless steel, unpainted). These were described by Ron Ghosh as "enormous, slow and a pain to use".

R. Mossbauer (Dir. of the ILL) was very friendly with Wiedemann, the head of the Walter Meissner Institut (WMI) in Munich, trusting his judgement. They both decided to outsource the manufacture of ILL's cryostats to Stoehr, whose factory in Augsburg had been producing drums for the dairy industry. A. Heidemann thinks he had an influence on the design; during his sabbatical year at ILL from Garching he asked Mossbauer for a "top-loading", variable temperature cryostat for IN10, with a narrow tail (50 mm). When the various cryostats ordered by ILL were ready, Anton Heidemann and David Wheeler (recently arrived at ILL) went to Stoehr in Augsburg for the acceptance procedures.

The Stoehr cryostat for IN10 worked fairly well and was used over a long period, but thanks essentially to the major changes it underwent at ILL. Anton Heidemann remembers what was said of it at the time:

"Stoehr-Kryostaten muss man entstören, damit sie funktionieren" (Stoehr cryostats need to be de/stoehrbed, if you want them to work!)

The joke in German is based on the similarity between "Stoehr" and "entstören" (eliminate interference).

Klaus Gobrecht confirms the adage, adding that it took 4 weeks to get a Stoehr to work correctly. The major problems encountered by ILL with these devices were described in outspoken fashion in an exchange of letters [2]; they were certainly one of the factors contributing to the development of the orange cryostat.

Oxford Instruments cryostats (metallic light-blue, in the early days at least) these were a tardy development, associated with the cryomagnets.

1. Minutes of the cryogenics meeting (pdf - 385 Ki) of 22 March 1973, Dominique Brochier, ILL.
2. ILL note: "Cryostats pour les expériences" (pdf - 529 Ki), M. Jacquemain and D. Brochier, 8 October 1973.