Meeting note by A Foussat

Meeting : Anticryostats procurement within STAARQ test cryostat for MQ and MQYY magnetic measurements – 20/11/2019

Participants : V Parma, C Petrone, Dmitry Akhmedyanov, A Foussat (CERN), J.M Gheller, H Allain, C Lorin (CEA)

Agenda presentations, Draft specifications :

H Allain presented the design of the anticryostats within STAARQ future test cryostat for MQ and MQYY magnetic measurements.

Main point of discussion about the AC design

The total height of the magnet assembly including the insert is 7.65 m. The useful magnet length suspended under the lambda plate is 6.3 m with a fixed insert height of 1.3 m and diameter of 750 mm. The operating pressure is 1.3 bar and maximum design pressure is 4 bars, category IV PED.
The HTS current leads has resistive part cooled by GN2.
The lambda plate is divided in two parts to cope with various anticryostats diameter. There is insulation vacuum between the internal MLI covered tube and outer tube.
The heat load in 4.5K is estimated at 3.6 W and 2 to 3.2 W/m respectively for MQ, MQYY.
The main difference with the common LHC anticryostat design is that in this vertical design there is no cold beam tube to support the AC tubes.
Ten layers of MLI shall be used to reduce by factor the heat loads.
It was mentioned that there is a good margin of factor 4 onto the design heat load (80 W) of the HEX He saturated.
In order to accommodate the thermal shrinkage of the outer tube some three independent bellows are used. They have been chosen short enough as easier to integrate
The annular G11 spacers are designed with alternated inner and outer surface supports to tube with a longitudinal passage for the feeding GHe tube. Each side support are installed 120 deg apart.
A centering head jig made of teflonÒ is used during the insertion of the shaft into the AC inner tube.

Discussion on existing AC design open items with CERN

The top ISO F DN100 bell assembled on AC as designed can be adapted to the required diameter of the measuring magnetic per C Petrone request
CEA envisages to use GN₂ to control temperature of the annular space instead of GHe considering risk of plugging the capillary.
The lifting attachment point on the bell area shall be checked to be able to lift the assembly of anticryostat load and its equipped measuring shaft. The last tube section of 1.3 m has a larger wall thickness.
the sequence of assembly of the magnetic shaft into the AC has to be confirmed : either horizonthal or vertical MM shaft assembly which has some impact on the upending handling jig. The horizontal assembly of the shaft seems more appropriate according to C. Petrone.
It was pointed out that the AC itself needs some centering device to keep the wall apart from the coil bore sides. Those equipments need to be interfaced at extremity end plates of MQ, MQYY.
The impact of the local permeability of the GHe capillary onto the magnetic measurement shall be checked.
The type of heaters to regulate temperature in continuous mode of the inner AC tube is not yet fully selected. Some Minco zigzag heater type are proposed by CEA but it was pointed out that the influence on magnetic measurement shall be evaluated. The LHC AC type used some wire routing layout which is optimised for magnetic field cancellation.

Specifications document and procurement strategy:

The shafts and anticryostats are needed from February 2021 to make assembly rehearsal in te MQYYM cryostat layout. If not available the next time window would be in June 2021 at the start of the MQ or MQYY measuring campaign.
The contract specification foresee that a main contractor supplier procure all main inner AC tube components make first preassembly to be leak tested. A Hold point is planned where CEA personnel will install the instrumentation and heaters. Although mentioned as a more risky way of procurement it was confirmed this is the only option left as there is no resources available to do this components assembly either at CEA or at CERN premises, to be endorsed by management. The intervention at contractor premises is then followed by the insertion and final leak tightness test.
The corresponding estimate budget for 4 long AC tube has to be identified at MSC for launching departmental request and procurement tender