Annuals Reports

Key points

What follows is drawn essentially from the first 12 ILL Annual Reports.

The beginning of the cryogenics service


  • Recruitment of Gabriel Prati, TBT technician


  • Management realises the time that had been lost before deciding to constitute a sample environment group.
  • J. Kalus works on the design of a cryostat for studying phonons as a function of temperature.


the reactor's first divergence

  • Recruitment of Serge Pujol, technician with TBT.
  • Retirement of Dominique Brochier (CNRS/CRTBT thesis student).
  • At the end of 1971 cryogenics had 1 engineer and 3 technicians.
  • ILL orders commercial cryostats from France and Allemagne (no other details). These were almost certainly from THORAir Liquide/TBT and/or SBT (France); Stöhr (Allemagne).
  • There was no helium recovery system in place, so ILL was losing all its gas.

The first cryogenics laboratory; and already thinking dilution


  • Creation of a cryogenics laboratory.
    Klaus Gobrecht remembers that the cryogenics was attached to the reactor, with offices on the fourth floor of ILL 4. Later Mossbauer created a "Sample Environment" service including cryogenicshigh temperatureshigh pressureshigh fields which was attached to the "Instruments" service (J.-C. Faudou) and then later to EDEX (D. Wheeler).
  • Serge Pujols builds the first ILL cryostat at the CEA/SBT for Anne Ermolieff.
  • ILL orders 3 fixed-temperature helium cryostats and 6 variable-temperature cryostats.
  • Installation of the liquid N2 distribution system (Oct 72: a 2800-litre tank in the guide hall) and the liquid helium system (10 100-litre tanks).
  • Contract with the CENG and CNRS for the supply of liquid helium.
  • Construction of the helium recovery system (Sept 1972).


  • Extension of the "Récup." to the other hitherto non-equipped experimental areas
  • There are 14 cryostats in use, but the annual report notes that ILL should have four times more if compared to other labs of the same size. ILL buys 13 more cryostats. D5 is fitted with a THOR cryostat.
  • Contract signed with CNRS/CRTBT (May 73) for the construction of a dilution cryostat. Testing starts at the end of the year.
  • An order is placed with Oxford Instruments for a cryomagnet ("a superconducting cryostat") for D3 and D5, but there's no mention of its details.

The famous Orange cryostat takes its first steps


  • Klaus Gobrecht (PhD student at the CRTBT) is recruited in April 1975 by Yves Droulers (1st Head of the ILL reactor) to assist Dominique Brochier.
  • 34 commercial cryostats in operation at ILL, but only six "full range variable-temperature" models.
  • The dilution cryostat bought from the CNRS reaches 0.055 K.
  • 6 months of development, to build a "full range (1.5-300 K) variable cryostat, top access, light, small, with very large holding time, easy to operate" It's the birth of what was to become the famous Orange cryostat.


  • 43 commercial cryostats in operation.
  • The Orange cryostat is proving its worth, but there's more work to be done on its name: "The 1.5 to 300 K variable temperature cryostat, with access to the sample from above, lightweight, compact and with a very long holding time (5 days) offers high speed of temperature variation and sufficient stability (< 0.01 K)"... Ouf !
  • The cryogenics service still has doubts as to its future however. "It should, however, not be forgotten that there are on the market closed circuit cooling machines which are very reliable and permit temperatures of 8 to 10 K to be obtained. These machines do not consume any cryogenic liquid and their cost is thus recovered in less than 2 years."
  • Dilution (T < 1 K): Development stops, following the death of Gabriel Prati in a light plane accident on the Pas de la Coche.
  • Cryocooler: D9 is fitted with a mono-stage Displex reaching 45 K, allowing crystalline structures to be measured up to 50 K under real measuring conditions.

The early days of the cryocoolers


  • ILL has 48 cryostats (1.45 cryostats per instrument) and we're almost touching the figure aimed at in the 1973 report.
  • 70% of experiments require a cryostat.
  • Everybody wants an "ILL cryostat" (not yet known as "Orange"), but there are only five in existence!
  • First mention of "Closed-circuit refrigerators". They can only reach 9-10 K and the scientists aren't interested. This is when Mogens Lehmann fitted one to the D9 diffractometer
  • New technicians arrive for the TBT (Jean-Louis Ragazzoni, soon to be assisted by Peter Suttling). The dilution cryostat is modified and improved, and is back in operation.

Cryomagnets arrive on the scene


  • ILL is now running 50 cryostats, 10 of which are cryocoolers.
  • Dilution cryostats: "Measurements at very low temperature are now, if not easy, at least possible, thanks to the efforts made since 1977."
  • A first 5-Tesla cryomagnet (superconducting magnet) is purchased. A 10-Tesla cryomagnet is ordered. A technician was affected full-time to this equipment (Peter Suttling).
  • The calibrated impedance used to measure the helium flow is built into the cold valve needle. Cleaning time plummets from 24-48 hours to a matter of minutes.
  • D10: new helium flow cryostat providing a temperature range of 4 K to 300 K, and without angular constraints. To minimise heat loss, the capillary carrying the helium is magnetically suspended within the transfer tube.


  • Programme to introduce 10 orange cryostats a year.
  • Development of a system for changing the sample without having to stop the Displex cryocooler.

Invention of the dilution insert


  • First mention of "3He systems" reaching 0.5 K - Karl Neumaier's dilution inserts.
  • The Orange cryostat: signature of a manufacturing licence agreement with AS Scientific.


  • ILL focuses on Neumaier's "pocket dilution cryostats", compatible with the Orange cryostats and reaching 40 mK.
  • Testing starts on a 5 K superfluid helium ultra-cold neutron source.

Rapid sample changing


  • Bottom-loaded rapid dilution cryostats (ILL-CRTBT). 1st simple exchanger model - giving 55 mK in 3 hours. A 2nd model, with an improved exchanger, aimed at 10 mK in 5 hours.
  • The "closed helium circuit" models originally rated at T=10 K are now at T=12 K, which is more realistic.


  • The Orange cryofurnace: the same cryostat now covers a temperature range of 1.5 K to 500 K.
  • New aluminium-stainless steel joints.


  • The ILL-CRTBT rapid dilution cryostat: the target of 10 mK in 5 hours is reached
  • 5 "Neumaier" dilution inserts are built (2 for NIST, 1 for Rutherford, 2 for the ILL).
  • High demand for very low temperatures. ILL is obliged to borrow a dilution cryostat and operator from the CRTBT.
  • Prototype available for automatically controlling the cold valve.


  • More and more demand for very low temperatures (263 days of measurement).
  • Thanks to rapid sample-changing up to 3 samples could be measured in the same week.

CRYOPAD, a new spectroscopy


First mention of CRYOPAD, for which a special cryostat is built and tested.


  • The Godfrin project (to become DRILL): a high-power dilution cryostat. Tested at 20 mK.
  • A new helium flow cryostat  for D10. The first one is in routine operation. The second covers temperatures from 1.7 K to 573 K.
  • Work to develop the cryostats continues: new cold valve, new 3-way valve, new safety valve.


  • CRYOPAD (Cryogenic polarization analysis device), for zero field neutron polarimetry, enters into operation.
  • Development with the CRTBT of a dilution cryostat insensitive to gravity. A cryostat starts  up on D10.
  • The Godfrin project (to become DRILL): the cryostat reaches 5 mK.


  • A new pneumatic control automatic cold valve. One more step towards automating liquid helium cryostats.