AMICI

Context:

The cryogenic infrastructure, which includes two tests areas respectively located in the buildings 103 and 106 at IPNO, consist of the following equipment's:

A helium liquefier (Linde L70)
Helium pumping systems for tests in superfluid helium
Gaseous helium recovery for recycling after use
A cryogenic test facility #1located in building 103
A cryogenic test facility #2 located in building 106
Three test stands with vertical cryostats (ID: 800 mm, 350 mm and 125 mm)
Several cryogenic inserts for cavity testing, material and component characterization at low temperature
A facility for calibration of cryogenic thermometers in the range 1.6 K -300 K

Production of liquid helium and recycling of gaseous helium

Chemical etching facility

Production of liquid helium:

Liquid helium is produced at IPNO using a commercial helium liquefier Linde L70: the liquefier is in operation since 2009 with a liquefaction rate of 70 l/h. More than100 000 l of liquid helium (LHe) were produced since 2009, including 50 000 l of LHe used for Spiral2 project.

Linde L70 helium liquefier

Recovery, compression and recycling of gaseous helium:

Due to heat load, during the cryogenic tests the liquid helium is evaporated. The resulting gaseous helium is then recycled after use. Helium gas is recovered, 8 compressed then stored prior to be purified and re-liquefied. The Gaseous helium storage capacity corresponds to 3000 liters of liquid helium

Gaseous helium inflatable balloon

Three stages room temperature helium gas compressor

Pressurized (200 bars) gaseous helium

Helium pumping systems:

The two cryogenic test facilities of building 103 and 106 allow experimental test with saturated liquid bath at subatmospheric pressures. Rotary vane pump and roots pumps are used for reducing vapor pressure of liquid helium down to xx mbar corresponding to a bath temperature of 1.6 K.

Helium pumping systems

Available refrigeration power at 2K (Bldg 103 and Bldg 106)

Test area	1	2
Site 1	10W@2K	40W@2K
Site 2	20W@2K	80W@2K
Site 3	40W@2K

Cryogenic test facilities and test stands

Cryogenic test area #1- Bldg 103

This area consists of 4 tests stand where cryogenic tests are performed in vertical cryostats (ID: 800 mm, 350 mm and 125 mm) from 300 K down to 1.6 K. These experimental facilities allow low power RF test of SRF cavities resonating at the following frequencies: 88 MHz, 352 MHz, 704 MHz, 1.5 GHz, 3 GHz, 3.8 GHz and 5.6 GHz

Vertical test of cavities of a ESS double spoke cavity (f=352 MHz)

Cryogenic thermometers calibration facility

The cryogenic thermometers calibration facility was designed and constructed in the frame of the Large Hadron Collider (LHC). More than 5000 thermometers were calibrated with this facility. These sensors (1800 sensors for the magnets and the 3200 for the cryogenic lines and equipment) are used for cryogenics and operation process of the LHC.

Features:

Calibration is performed by comparison to reference sensors: the thermometers to be calibrated are mounted on the same thermostatic copper block as the 4 reference thermometers (4 RhFe working temperature references)
Temperature range: 1.6 K-300 K
Absolute accuracy of ± 5 mK from 1.6 K to 4.2 K
Relative accuracy: 1 % of temperature T in the range 4.2 K -300K.
Capability: up to 90 thermometers
Temperature of the thermostatic OFHC copper block is regulated (PID) by means of a heater attached to the block and helium cooling loop.
Automatic data acquisition and analysis (fit of experimental data)
Calibration data saving in a dedicated database
A vapor pressure bulb soldered on the calibration block and connected to a pressure sensor is used as a primary temperature reference for in-situ control of the working standard thermometer calibration

Cryostat and calibration cryogenic insert

Cryogenic thermometers calibration

Related test stands:

Low temperature material characterization used for the fabrication of SRF cavities and ancillaries

Two test stands with several cryogenic inserts are used for material and components characterization at low temperatures. They allow the measurements of electrical, superconducting, electromechanical and thermal properties at low temperatures. One insert is dedicated to R&D on special sensors and electronics for investigation of anomalous RF losses and phenomena limiting the performance of SRF cavities (e.g quench detection via second sound events, surface thermometry, field emission probes).

Thermal conductivity test cell and its cryogenic insert

Electrical resistivity and RRR measurement

The RRR is defined as the ratio between electrical resistivity of the material at the ice point (T=273K) and the residual electrical resistivity ρ measured at the liquid helium normal boiling point (T=4.22 K). These measurements is performed using the standard DC four probes method with reversing the sensing current to eliminate parasitic thermoelectric voltages. Electrodes are clamped to the flat test sample by means of copper-beryllium springs (contact pressure: ~12 Bars). The test sample (length: 80 mm), is equipped with a calibrated Cernox thermometer (T=1.6K— 300 K) and immersed in a saturated liquid helium bath at T= 4.2K. The sensing current of 1A, is delivered by a precise standard DC voltage supply, is on-line measured via the voltage drop across a precision resistor