MICE Collaboration Meeting 17 CERN 21 – 25 Feb 2007 Summary on Magnet & MICE Integration talks By Oxford University

Summary of the parallel session on Cooling Channel magnet and integration Talk by Mike Green on liquefaction of hydrogen & helium using small coolers Status of the AFC technical specifications – prepared by Elwyn Baynham Status of the B-field probes by Frank Filthaut from NIKHEF Window thickness measurement using feather weight probe at Fermilab by Michael Wojcik Status of the Hydrogen R & D at RAL– prepared by Tom Bradshaw already summarised in Chris Nelson’s talk yesterday and is not repeated here. Outline design of the MICE Cooling Channel vacuum system by myself MICE Drawing system – a reference to the Cooling Channel drawing system. This was not discussed as Chris Nelson was not present

The Use of Small Coolers for Hydrogen and Helium Liquefaction Michael A. Green Lawrence Berkeley Laboratory

Mike Green will have a separate talk on this straight after this talk

AFC Technical Specification – towards tendering

AFC Specification Scope of supply Basis – manufacturing design and build to Specification based on: Technical Specification CAD model + definition drawings Applicable documents – standards and safety codes

AFC Specification Scope of supply - manufacturer Overall vacuum vessel AFC solenoid coils in magnet vacuum vessel Vessel will have mountings for absorber and secondary absorber vacuum window Service turrets Solenoid turret equipped with cryocoolers, condensing pot, current leads and instrumentation Hydrogen turret equipped with cryocooler, condensing pot + internal pipework to interface with absorber Large end plate to define absorber vacuum and provide mounting for absorber vacuum window Support stand to interface with the MICE rails

AFC Specification Scope of supply - customer CAD model and definition drawings for final design and manufacture Instrumentation definition Interface to the hydrogen absorber – mechanical and instrumentation to be transferred outside the cryostat Definition of the control interfaces to MICE Vacuum pump set for test at works Power supply for test at works

AFC Specification Tests by manufacturer Stage testing of coil insulation during manufacture Stage testing of vacuum vessels and cryogenic pipework during manufacture and assembly Final module tests Magnet Ramp up to design current – hold - ramp down flip and non flip modes Demonstration of safe quench operation Inductance measurements Measurement of field on axis in non-flip (solenoid) mode Cryogenics Full tests of thermal performance for cooldown and cryocooler operation Vacuum and electrical system tests of final module

AFC Specification Status and next steps Specification is basically complete and will be submitted to the TB for review Design issues under consideration and discussion minor changes or additions relating to interaction of magnetic fields with current leads and coolers acceptance criteria for magnet and absorber cryogenic systems These will be resolved shortly but should not influence approval by the TB Meeting with RAL contracts is scheduled List of manufacturers will be prepared A few points to highlight here …..

Outer Vessel Shell …………….. the vessel shell will provide the main interface to the MICE Experiment. The vacuum sealing at the flanges will be made by ‘O’ rings.[MSZ1][MSZ1] [ MSZ1]I don’t like this, as it is incompatible with Neutrino Factory operation. Can we make provision for a welded or metallic seal at Step 6, say?[ MSZ1] Cryogenic services …………… the cryocoolers will be required to operate in the background magnetic field of the solenoid. The magnetic field levels at the cryocooler are specified in Annex 1.6. Shielding of the cryocooler may be required. Further details can be supplied as necessary. The baseline design shows the use of a pulse tube cooler. The baseline design shows the use of a pulse tube cooler, the manufacturer is free to propose an alternative technical solution.

Powering and Magnet Quench Protection ……………… in the MICE cooling channel the three AFC modules will be powered in series as shown schematically in Figure 8. Each solenoid will be equipped with a system of resistors and diodes for quench protection. The parameters specified for powering and quench protection are given in Annex 1.9. The quench peak temperatures and voltages are based on analysis which included quenchback from the winding mandrel as part of the protection mechanism. The customer can supply details of this analysis on request. The manufacturer will define and justify the quench protection system for approval by the customer

B-field probe status Frank Filthaut Radboud University / NIKHEF

Sensors attached to tracker support frame and measuring field in tracker volume: OK Other sensors: questions about placement * Inside solenoid bore: logistic (integrity various (vacuum) enclosures) and/or safety issues (proximity to hydrogen), however, full sensitivity to relevant magnet field * Outside cryostat: will measure stray field only (~ 500 Gauss?), but will avoid issues described above It was remarked that for AFC, placement within the bore would in any case be impossible. The possibility of positioning inside the cryostat was discussed, but this appears very impractical. So at least for the AFC, placement outside the cryostat appears to be the only alternative.

One important side effect of mounting sensors outside the cryostat was discussed in some detail: this seems relatively straightforward when no magnetic materials are present, but when these have to be counted with, the dependence of the measured field on magnet current settings becomes nonlinear. Even when these sensors are primarily useful for monitoring purposes (as opposed to precision absolute measurements), the question arose how useful the sensors would be in this case. Given the potential issues with shielding cryocoolers, it was decided to ask Holger Witte to run through some scenarios to learn more about the limitations.

Note that small hardware revisions would be required to make the existing sensors suitable for use in the stray field outside the cryostat. Questions about quantities: 36 sensors have been produced (although not yet calibrated) so far. Michael suggested that 4 sensors per coil (i.e., 4*18=72 sensors) might be more appropriate. This would count 5 coils per tracker. There exists a possibility to request the production of more sensors. It seems this should be done.

Window thickness measurement by Michael Wojcik of IIT

CMM Touch Probe Specs: Trigger Force < 10 mg ~ 0.1 mN Measuring Error ~ 1 µ m Mounted on an table with a robotic arm.

Probe Setup

Window measurement 1.Create a coordinate system using spheres attached to the window 2.Measure points on the concave side and convex side 3.Take the difference in the measurements to find the thickness So they expect to get something like…

Measurement Should Resemble Touch Probe Al Window Tangential axis The probe touches one side then the other side on the axis tangential to the window

First Set of Data

The Second Set of Measurements

Third Set of Data

Window from RAL

A Zero Problem There is a average of 10 micron difference of thickness at center of window. Why?

Sources of Error ~1 µ m from probe Touch probe difficulties Expected Touch Actual Touch Wrong touch location Wrong touch Axis Expected Touch Actual Touch

Action agreed A task force consists of Steve Virostek, Michael Wojcik and Wing Lau was set up to bring this to an earlier conclusion. We have agreed the following actions: Wing to write up a measurement requirement and to specify the locations of the measurement points on the window Steve to review this write up; Michael to stamp a datum mark on the existing window flange so that all subsequent measurements could be referred to a common datum point; Michael to repeat the window measurement and send results to Wing for assessment; The window is then shipped to LBL for a second measurement using similar CMM machine which LBL had acquired recently; Wing to discuss with Steve on the validity of these results and to outline future QA procedures

Cooling Channel vacuum system

The above system has a potential breach of safety issue It was agreed that the vacuum pumping of the tracker & AFC space, though requires regular backing, should have its own manifold and pumping unit;

The above system has a potential breach of safety issue It was agreed that the vacuum pumping of the tracker & AFC space, though requires regular backing, should have its own manifold and pumping unit; We agreed to look into the safety implication of have the 3 hydrogen buffer joined to a single pumping unit. The ideal solution is for each of the AFC h2 buffer to have its own pumping unit

MICE drawing system – a reference to the Cooling Channel drawing system

General arrangement drawing Assembly drawings Sub-assembly drawings Parts drawings Sub-parts drawings

AFC General Arrangement drawing General arrangement drawing Assembly drawings Sub-assembly drawings Parts drawings Sub-parts drawings

AFC Assembly drawing - AFC Cryostat -- Hydrogen system General arrangement drawing Assembly drawings Sub-assembly drawings Parts drawings Sub-parts drawings

AFC Assembly drawing - AFC Cryostat -- Hydrogen system Tracker module -- Diffuser assembly drawing General arrangement drawing Assembly drawings Sub-assembly drawings Parts drawings Sub-parts drawings

MC-TM-GA-01

AFC Sub-assembly drawing - AFC Vacuum vessel General arrangement drawing Assembly drawings Sub-assembly drawings Parts drawings Sub-parts drawings

AFC Sub-assembly drawing - AFC Vacuum vessel Tracker Module -- Diffuser sub-assembly General arrangement drawing Assembly drawings Sub-assembly drawings Parts drawings Sub-parts drawings

AFC Parts drawing - AFC vessel Outer Shell General arrangement drawing Assembly drawings Sub-assembly drawings Parts drawings Sub-parts drawings

AFC Parts drawing - AFC vessel Outer Shell Tracker Module -- Diffuser parts drawing General arrangement drawing Assembly drawings Sub-assembly drawings Parts drawings Sub-parts drawings

Tracker Module -- Diffuser sub-parts drawing General arrangement drawing Assembly drawings Sub-assembly drawings Parts drawings Sub-parts drawings

Example of how this is organised is on the Oxford MICE web page

Remarks Decision to adopt this drawing system to MICE as a whole rests on the MICE project engineer, Chris Nelson. As the Cooling Channel Integration engineer, I would insist on all the drawings related to the Cooling Channel components be constructed in this way.