17 March 2005Edda Gschwendtner1

MICE Cooling Channel:Can we predict cooling to 10-3 ?

Edda Gschwendtner

Challenge Systematics Cooling Channel Beam Line Summary

17 March 2005Edda Gschwendtner2

Challenges of MICE

Operate RF cavities of relatively low frequency (200MHz) at high gradient (up to16MV/m) in highly inhomogeneous magnetic fields (1-3T)

Dark currents (can heat up LH2) breakdowns Emittance measurement to relative precision of 10-3 in environment

of RF background requires low mass and precise tracker Low multiple scattering Redundancy to fight dark current induced background Excellent immunity to RF noise

Hydrogen safety substantial amounts of LH2 in vicinity of RF cavities and SC magnets

17 March 2005Edda Gschwendtner3

Goal of MICE

Science fiction example: MICE measures (ε out/ε in)exp = 0.904 ± errstat

and compares with (ε out/ε in)sim = 0.895

Try to understand the difference.

10% cooling of 200MeV/c muons

With measurement precision: Δ (εout/ εin) = 10-3

Theory uncertainties: Model and simulation choices

Experimental uncertainties: Design of detectors/cooling elements

17 March 2005Edda Gschwendtner4

Sources of Experimental Systematic Uncertainties

Particle tracker Assume: tracker can give precision of particle position and momentum

that won’t contribute significantly to the error. Particle ID

Assume: Particle ID < 1% error Cooling channel / detector solenoid

Main source of systematic errors! Should be under control to a level such that up to 10 independent

sources of systematics will be < 10-3 ( each of them < 3 ·10-4) (Beam line)

This talk!

17 March 2005Edda Gschwendtner5

Cooling Channel

three Absorber and Focus Coil modules (+ three LH2 handling systems) two RF Cavity and Coupling Coil modules (+ RF power systems) power supplies, field monitoring, and quench protection for magnets infrastructure items vacuum systems (pumps, valves, monitoring equipment)

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How to Handle Systematics

Design considerations Define tolerances Monitoring Calibration measurements with the muon beam

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Quantity Tolerances Monitoring Calibration with muon beam

RF CAVITIES RF field 3·10-3

measure E to

E/E= 3.10-3

Measure phase

measure energy of muons vs RF phase before and after cooling channel.

ABSORBERAmount of absorber (in g/cm2 )

3·10-3 = 1mm/35cm

Cryogenics…

Density through T & P

measure energy loss of muons for

0 absorber, 1 absorber, 2 absorbers with RF off.

MAGNETS

Positions of coils some mm alignment transfer matrix: e.g.:

(pt, pL, phi, x0 , y0)in <-> (pt, pL, phi, x0, y0)out

measure with no RF and empty absorbers each time one changes the magnetic set-up.

Currents some 10-4 amp-meter

Magnetic field some 10-4 magn. probes

Cooling Channel

NB thickness of H2 absorbers cannot be easily measured in situ (safety

windows are in the way)

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RF dark currents were measured at Fermilab on 805MHz cavities in magnetic field Extrapolation to 201 MHz Simulation of RF backgrounds Will resume tests on 201 MHz prototype in spring 2005

RF Cavities I (Calibration & Design)

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RF Cavities II (Monitoring)

Monitoring of: Voltage, phase and temperature in each

cavity temperature of Be windows Cavity position and alignment w.r.t.

solenoid cavity and cryostat vacuum, incl.

couplers cryopump performance (P, compressor

control, valve status) roughing system (pump status, pump

vacuum, pump valves) tuner hydraulic reservoir pressure and

dynamic control

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ΔE = (Eout -Ein )(GeV) of muons

measures ERF(t)

RF Cavities III (Calibration with Beam)

(Simulation by P. Janot in 2001 at 88 MHz)

ΔE1 -Eloss + ERF ΔE2 -Eloss - ERF

ΔE1

ΔE2

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AbsorberMonitoring of:

H2 gas system and He gas system Pressure gauge

LH2 reservoir at 1st stage of Cryocooler Thermometers Level sensor 2 Heater

Hydrogen absorber Thermometer Level sensor

Absorber windows Thermometer Heater

Safety windows Thermometer

Absorber vacuum and Safety vacuum Pressure gauge Pirani & cold cathode gauge Mass spectrometer → Windows will be measured before and after

a run (by photogrammetry or laser) to verify that they did not suffer inelastic deformations

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- STEP I: spring 2007

STEP II: summer 2007

STEP III: winter 2008

STEP IV: spring 2008

STEP V: fall 2008

STEP VI: 2009

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Magnets I

SC Coils

Magnetic

sensors

3 hall probes

Positioning holes

Variety of currents and even polarities Field maps: not simply the linear superposition of

those measured on each single magnet Forces are likely to squeeze the supports and

move the coils in the cryostat Measure magnetic field with field probes

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Magnets II

Monitoring of : current in each individual supply (incl. trim supplies, if any) magnetic field at external probes (Bx, By, Bz); proposal is 4 probes per coil quench protection system cryocooler, coil temperatures He level sensors correlations between current, field, and temperature need to

be obtainable as a diagnostic tool cryostat vacuum

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dipole

dipole

quads solenoid

quads quads Diffuserbar-code reader?

v

vv

v

vv

V V

Target

ISIS:-BLM-Cycle information

Solenoid Cryogenics & control system

MICE

DiagnosticsDAQ Control System Hybrid

Beam Line I

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Beam Line II Beam Line:

All magnets Qs (9), Ds(2), decay solenoid Currents

Alarms on temperature, cryogenics, vacuum etc Target:

Synchronisation inputs ISIS Machine Start (once per injection) ISIS clock (200 kHz)

Control Settings insertion depth insertion time

Operational monitors Up to 8 temperature measurements per cycle (inner coil, outer coil,

cooling water inlet, water outlet, ...) Target position

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Summary

Systematics must be understood to 10-3 level. Main sources are Cooling Channel

Detailed monitoring is in most cases possible and being designed.

Muons will provide very powerful cross-checks for themselves (energy loss, energy gain, transfer matrix…)

Dedicated ’monitoring runs’ will be possible and necessary. Strategy being discussed.

10% cooling of 200MeV/c muons with measurement precision: Δ (εout/ εin) = 10-3