LH2 Absorber Heat Load and Homeostasis

What has happened before…

1. Huge LH2 volumes, low heat deposition: Bubble chambers

2. Small LH2 volumes, low heat deposition: FNAL E866

…here density fluctuations are an issue:3. Medium volumes, large heat deposition: Sample,

Slac E158Our challenge:

Large heat deposition and beam path is through entire volume of absorber!1. Liquid must move everywhere2. Need gauge of temperature and density uniformity

Sample and E158 Targets

E158 target ~60 liters Sample target ~25 liters

Beam size ~ 2mm: defines small turbulence scale, and is small part of total volume

Calibration was total measurement

Muon Ionization Coolingx x

z zP1

P2

absorber

accelerator accelerator

absorber

P1

With transverse focussing (solenoid) :

Rμ3

trans

xx

LmEβ

βf

L

ε

dz

dε

Multiple scattering

reductionemittance

max.forβLow

Heating term (Mult.Scatt.)Cooling term +

lengthradiation:LBe

c2pβ

dE

dzEβLv/cβ

R

2trans

RF cavity

RF cavity

Need to minimize heating!

Internal heat exchange: Convection is driven by heater and particle beam.Heat exchange via helium tubes nearabsorber wall.

Flow is intrinsically transverse.

Convection absorber design

Output from 2-dim Computational Fluid Dynamics (CFD) calcs. (K. Cassel, IIT). Lines indicate greatest flow near beam center.

Qualitatively demonstrated but parameters need to be measured. Prototyping of this design is being done by Shigeru Ishimoto et al at KEK.

Forced-Flow Absorber Design

Mucool ~ 100W (E. Black, IIT) Large and variablebeam width =>large scale turbulence

Establish transverseturbulent flow withnozzles

External Heat Exchange:

For ~ 8W/cm heat deposition, need to cycle 0.05 volumes/sec LH2 (e.g. 240W/30cm).

Nozzle design complicated - needs prototyping and testing.

So far… Three dimensional LH2 flow

simulations (W. Lau)

Testing 3-dimensional

simulations with water

flow test at NIU

1. Nozzle arrangement2. Heat application3. Cryo tests

Schlieren testing of convection flow

(water) test at ANL

Flow Tests Proposed

Three test modes (E.Black):

1. Absorber manifold , two plastic windows:Absorber filled with water at room temp. – the pattern of flow will be photographed by circulating water from inlet to outlet using a luminous die injected at inlet. Hard to get real window volume flow picture this way.

2. Absorber manifold, one plastic windows, one aluminum windowAbsorber subjected to a heat source. Infrared pictures taken (for forced-flow and convection absorber type). Distortion from heat distribution in window.

3. Absorber manifold , two thin Al windows, cryogenic:Absorber integrated into a cryo system, operating in test mode with extreme temperature and pressure variations considered for safety.

Yet to have a definitive determination of adequate probe placement.

Infrared flow test setup

Now, the questions…

1. What computations are helpful?

2. Are flow/convection predictions “linear”?

3. What tests will be useful, and how quantitative can they be?

4. What level of instrumentation will convince us of sufficient temperature uniformity?

5. How will convection and force-flow models be evaluated?

At this meeting…

Let’s decide what activity to pursue that:

1. Makes sense for the LINAC Cryo program next year

2. Contributes substantively to the MICE tech. review meeting in Oct.