Mucool LH2 Absorber Progress and Pauses Mary Anne Cummings FNAL August 12, 2002

Cooling channel requires minimum “heating”  Low Z material  maximize radiation length  Minimize window thickness/Z while retaining structural integrity  Nonstandard window design Absorber Heat Management  Refrigeration: W heat deposition from beam (~8W/cm)  Temperature and density stability: LH2 circulation  Novel flow and convection schemes Mucool LH2 Absorber Issues Safety  No LH2/O2 contact: containment, ventilation, controls  No ignition sources: instrumentation must be “safe”, RF cavities “benign”  New instrumentation technology emittance eqn.: Design/test drivers:

“FNAL” Progress 1.Non-standard absorber windows designed 2.Non-standard vacuum containment window designed 3.5 & 9.5 mil thin windows manufactured 4.Correct FEA analyses completed with predictions for window performance under pressure 5.Photogrammetric techniques developed for volume measurements 6.Photogrammetric techniques developed for window pressure test performance 7.Window predictions and data consistent! 8.Test Area proposed and ALMOST on “mass shell”! 9.Test Area Absorber system designed.

“Offshore” Progress 1.Convection prototype built 2.Convection prototype cryogenically operated 3.Convection calculations 4.Three dimensional flow test demonstration 5.Schlieren test program started 6.NIM Articles in progress 7.Window predictions and data consistent!

The issue: A non-standard thin window design  No closed form expression for maximum stress vs. volume pressure  FEA (finite element analysis): geometry stress material strain volume pressure displacement Window tests } Procedure (for manufacture quality control and safety performance) Three innovations:  Precision measurement of window  photogrammetric volume measurements  FEA predictions  inelastic deformation, 3 – dim included in calcs.  Performance measurement  photogrammetric space point measurements

“Non-standard” thin windows Exploit the structural stability of the spherical cap with a tapered/inflected connection to a solid flange Modified torispherical window (Black/Cummings) “Bellows” inflected window (Black/Lau) XiXi t diameter R rr

How to determine the “thinnest” thickness 1.Two different radii of curvature 2.Possibly not concentric Modified torispherical design If not at the center, where?

Manufacture to rupture 130  window “350”  window “340”  window Burst at ~ 120 psi 4. Burst at ~ 151 psi Cryo test Leaking appeared at 31 psi..outright rupture at 44 psi! 1.

CMM vs. Photogrammetry 1.Contact vs. non-contact measurements 2.“Several” vs. ~ thousand measurements 3.Serial vs. parallel measurements 4.Larger vs. smaller equipment 5.Better fit to spherical cap.  Photogrammetry is choice for shape measurement

Strain gage vs. Photogrammetry 1.Contact vs. non-contact measurements 2.Smaller spot vs. extended length 3.No messy wiring on the window test setup! 4.Better systematics – no added material! 5.Better coverage!  Photogrammetry is choice for strain measurement

d 1AU r d p p scale bar fixed targets

Photogrammetry resolution convexconcave convex concave d R r Alignment of sides D’ Small triangle fit Use spherical fit of small triangles D =  m ( 5.5  m) + (- ~10  m)

Stress distribution at the yield point FEA Calculations Finite Element Analysis  Non-elastic region included  Three dimensios necessary for vibrational analysis Window/flange simulation Window/flange cross section FEA, non-elastic region included  Displacement vs. radius under pressure:  NIU photogrammetry results and FEA calculations

Window performance summary 1.Descrepancies between CMM and photogrammetry are larger than their intrinsic errors 2. Descrepancies between photogrammetry and FEA predictions are < 5%

Design of LINAC LH2 Absorber Beam Test x z   accelerator absorber Multiple scattering RF cavity Physicist’s vision Engineer’s vision

Heat Absorption and Temperature Maintenance 1.What are the usable predictions from simulations? 2.What are the meaningful measurements? 3.Radical changes: flat windows? Design: 1.What do we need for temp/density measurements? 2.Window heating 3.Strain gauging Monitoring:

Safety Review 1.Windows (absorber) holdup: MACC, FEA & data pts 2.Windows (Vacuum) holdup will be the same 3.Manifolds Mucool Responsibilities 4.Instrumentation Mucool 5.Cryogenics FNAL

The Near Program 1.MICE and FNAL LINAC program merge 2.Convection Absorber schedule for LINAC 3.Instrumentation and DAQ integration 4.The LINAC/MICE cooling cell designs

Experiment Signals- Absorber temperature12 pressure transducerssee under cryo 2 Photogrammetry/optical (??)2 laser occlusion sensor(??)4 piezo vibration sensors2 Optical fiber strain gauges2 bolometry44 O2 sensors 3per each of 5 flanges15 H2 sensors on exhaust line10 CCD camera 2 images MICE channels“N” #signals

Instrumentation 1.Temperature/density uniformity inside LH2 2.Safety instrumention inside vacuum area 3.Detectors for cooling measurements Safety Issues: 1. Limits the amount of energy/(area or vol) 2. Physical size of the signal feedthroughs 3. Seals from signals to electronics: wires fibers tubes