17 March 2005Edda Gschwendtner1 MICE Cooling Channel: Can we predict cooling to 10 -3 ? Edda...
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Transcript of 17 March 2005Edda Gschwendtner1 MICE Cooling Channel: Can we predict cooling to 10 -3 ? Edda...
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)
17 March 2005Edda Gschwendtner6
How to Handle Systematics
Design considerations Define tolerances Monitoring Calibration measurements with the muon beam
17 March 2005Edda Gschwendtner7
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)
17 March 2005Edda Gschwendtner8
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)
17 March 2005Edda Gschwendtner9
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
17 March 2005Edda Gschwendtner10
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
17 March 2005Edda Gschwendtner11
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
17 March 2005Edda Gschwendtner12
- STEP I: spring 2007
STEP II: summer 2007
STEP III: winter 2008
STEP IV: spring 2008
STEP V: fall 2008
STEP VI: 2009
17 March 2005Edda Gschwendtner13
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
17 March 2005Edda Gschwendtner14
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
17 March 2005Edda Gschwendtner15
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
17 March 2005Edda Gschwendtner16
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
17 March 2005Edda Gschwendtner17
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