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MICE LH2 Absorber Safety. Mary Anne Cummings Edgar Black (IIT) Abingdon, UK Oct. 30, 2003. Design considerations. Multiple scattering. x. x. P 2. P 1. q 2. q 1. q 1. P 1. accelerator. q 1. accelerator. z. z. RF cavity. RF cavity. absorber. absorber.

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Mice lh2 absorber safety
MICE LH2 Absorber Safety

Mary Anne Cummings

Edgar Black (IIT)

Abingdon, UK

Oct. 30, 2003


Design considerations
Design considerations

Multiple scattering

x

x

P2

P1

q2

q1

q1

P1

accelerator

q1

accelerator

z

z

RF cavity

RF cavity

absorber

absorber

Muons through matter can actually focus!

cooling

heating

  • Emittance eqn:

  • So, minimizing beam heating term by minimizing and maximizingLR.The design features of a cooling channel:

    • Hydrogen (lowest Z, highest LR) for the cooling medium.

    • Thin windows for the hydrogen absorbers.

    • LH2 absorbers placed in large magnetic fields.

    • additionally…

    • 4) RF between LH2 absorbers to restore forward momentum:

q2


Liquid hydrogen safety
Liquid Hydrogen Safety

  • For safe operation, have designed with the redundant requirements:

    • LH2 and O2 separation

    • The avoidance of any possible ignition sources in the vicinity of the hydrogen.

  • The four key features of the design with respect to safety are:

    • The window thicknesses specified based on safety factors of 4.0 for the absorber window and 2.5 for the vacuum window at maximum allowable working pressure (MAWP).

    • An argon-gas-filled jacket surrounding the vacuum chambers of the RF/coupling magnet modules and the hydrogen absorber/focusing magnet modules to minimize the possibility of oxygen leaking in and freezing on the absorber-system windows.

    • Separate vacuum volumes provided for the RF cavities, magnets, and LH2 absorbers.

    • Hydrogen evacuation systems using valved vents into external buffer tanks.


Mice cooling channel design
MICE Cooling Channel Design

  • Other safety concerns:

    • Magnet quenching, LH2 absorber stability

    • Any instrumentation must be “instrinsically safe”

    • Sufficient shielding from detectors/RF

    • Robust, simple failsafe systems

Compact environment


Absorber coil assembly
Absorber/Coil Assembly

  • Sufficient venting into evacuation tank

  • Secure plumbing attachments

  • Stable and repeatable placement of LH2 absorber inside magnet bore


Experiment installation
Experiment Installation

Coil

LH2 absorber

  • Accessibility in a compact, sealed environment

  • Certification of Windows-Absorber-Coil Assembly

  • Accurate component placement

Hydrogen storage

ISSUES:


Lh2 window r d
LH2 Window R & D

Photogrammetry:

Non-contact measurement of strain by calculating displacement

Strain gages

~ 20 “points”

Shape measurement at FNAL

Pressure tests at NIU

Photogrammetry ~1000 points


Absorber window test results

Window #

Test temp.

FEA results

Test results

Minimum window thickness (mm)

Rupture pressure (psi)

Window thickness from CMM (mm)

Measured rupture pressure (psi)

1

293K

0.13

48

0.114

42

2

293K

0.33

117

0.33

119

3

293K

0.345

123

0.345

120

4

80K

0.33

156

0.33*

152

2.

3.

4.

Absorber window test results

4 burst tests:

1.

Cryo test

Performance measurement (photogrammetry)

1. Room temp test: pressurize to burst ~ 4 X MAWP (25 psi)

2. Cryo test:

a) pressure to below elastic limit to confirm consistency with FEA results

b) pressure to burst (LN2 temp) ~ 5 X MAWP fromASME:UG 101 II.C.3.b.(i)

Discrepancies between photogrammetry and FEA predictions are < 5%


Certification procedures
Certification procedures

  • Windows to be tested/certified independently: both vacuum and absorber

  • Pressure tests of assembled absorber manifold

  • Assembly inside vacuum containment vessel or magnet bore

  • Survey of absorber position inside magnet

  • Cryo pressure test after absorber installation

  • Pressure test of vacuum vessel after installation

  • Nitrogen/argon purge of absorber and vacuum before LH2 fill and vacuum area evacuation.

  • Safety valve tests


Vacuum windows

  • FNAL Requirements:

  • Burst test 5 vacuum windows at room temp. to demonstrate a burst pressure of at least 75 psid (~5 bars) for all samples. (pressure exerted on interior side of vacuum volume).

  • Non-destructive tests at room temperature:

    • External pressure to 25 psid (~1.7 bars) to demonstrate no failures: no creeping, yielding, elastic collapse/buckling or rupture

    • Other absorber vacuum jacket testing to ensure its integrity

Vacuum Windows

Vacuum “bellows” window (34 cm diam):

No buckling at

1st yield (34 psi)

Internal pressure: burst at 83 psi


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