Transcript Powerpoint - the Muon Cooling Homepage at MPI Munich

Columbia University & the Max-Planck-Institute
Review & Status of Frictional Cooling
A. Caldwell, R. Galea, D. Kollar
• Principle
• Simulations
• Review of Nevis Experiment
• Outline next experimental steps at MPI
• Summary
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
Principle
Same as freefall and reaching terminal velocity
Gravity opposing friction
Muons energy loss in gas is compensated by applied
electric field resulting in equilibrium energy
• Need low energy ms below
ionization peak
• Here energy loss is a to T,
the faster ms lose energy
faster than slow ms
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
(Ionization Cooling)
Cooling aim/obvious problems
• In this regime dE/dx extremely
large
• Slow ms don’t go far before
decaying
d = 10 cm sqrt(T) T in eV
• m+ forms Muonium
• m- is captued by Atom
s(Mm) dominates over
e-stripping in all gases
except He
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
• Low average density
(gas)
• Apply EB to get
below the dE/dx peak
• Make Gas cell long as
you want but transverse
dimension (extraction)
small.
s small above electron binding
energy, but not known. Keep T as
high as possible

   dT 
F  q( E  v  B) 
r
dx
Oscillations around
equilibrium limits final
emittance
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
Phase rotation sections
Results of
simulations to
this point
Cooling cells
•Full MARS target simulation,
optimized for low energy
muon yield: 2 GeV protons on
Cu with proton beam
transverse to solenoids
(capture low energy pion
cloud).
Not to scale !!
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
 He gas is used for m+, H2 for m-.
There is a nearly uniform 5T Bz
field everywhere, and Ex =5 MV/m
in gas cell region
 Electronic energy loss treated as
continuous, individual nuclear
scattering taken into account since
these yield large angles.
Results:
• Simulation of previous
scheme yielded final beam
emittances of
2-6x10-11 (m)3
At yields of 0.001-0.003
m+/GeV proton.
• Yield could be better yet
emittance is better than
”required”
• Cooler beams
• smaller beam elements
• less background
• lower potential radiation
hazard from neutrinos
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
Baseline parameters for high energy muon colli ders. From “Status of Muon Colli der
Research and Development and Future Plans,” Muon Colli der Collaboration, C. M.
Ankenbrandt et al., Phys. Rev. ST Accel. Beams 2, 081001 (1999).
COM energy (TeV)
p energy ( GeV)
p’s/bunch
Bunches/fill
Rep. rate (Hz )
p power (MW)
m/ bunch
m power (MW)
Wall power (MW)
Colli der circum. (m)
Ave bending field (T)
rms p/p (%)
6D  (m)3
rms n ( mm mrad)
* (cm)
sz (cm)
sr spot (mm)
s IP (mrad)
Tune shift
nturns (effective)
Luminosity (cm2 s1)
0.4
16
2.5  1013
4
15
4
2  1012
4
120
1000
4.7
0.14
1.7  1010
50
2.6
2.6
2.6
1.0
0.044
700
1033
3.0
16
2.5  1013
4
15
4
2  1012
28
204
6000
5.2
0.16
1.7  1010
50
0.3
0.3
3.2
1.1
0.044
785
7  1034
1.7x10-10 (m)3
THE GOOD: Simulations include:
• individual nuclear scatters
• Muonium formation
• m- capture in H2 & He
• tracking through thin windows
• initial reacceleration
Sufficiently cool muon beams
THE BAD:
• Yields are somewhat low
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
THE UGLY:
• Large amount of free
charge which would screen
field
• Not simulated
Nevis Experiment already
reported at NuFact03
R.Galea, A.Caldwell, L.Newburgh, Nucl.Instrum.Meth.A524, 27-38 (2004)
arXiv: physics/0311059
•Perform TOF measurements with
protons
•2 detectors START/STOP
•Thin entrance/exit windows for a
gas cell
•Some density of He gas
•Electric field to establish
equilibrium energy
•NO B field so low acceptance
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
RAdiological
Research
Accelerator
Facility
Look for a bunching in time
•Can we cool protons?
 4 MeV p
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
Assumed initial conditions
•20nm C windows
•700KeV protons
•0.04atm He
TOF=T0-(Tsi-TMCP)
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
speed
Kinetic energy
Results of RARAF experiment
• Various energies/gas
pressures/electric field
strengths indicated no cooled
protons
• Lines are fits to MC & main
peaks correspond to protons
above the ionization peak
Experiment showed that MC
could reproduce data under
various conditions. Simulations
of Frictional Cooling is
promising.
Exp. Confirmation still desired.
Low acceptance but thicker windows was the
culprit
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
Frictional Cooling Demonstration at MPI Munich
• Repeat demonstration
experiment with protons
with IMPROVEMENTS:
• No windows
• 5T Superconducting
Solenoid for high
acceptance
• Silicon detector to
measure energy directly
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
Cryostat housing 5T solenoid.
Si Drift detector
 
E, B
He gas
HV Cable
Up to 100KV
Source
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
Where do we get protons?
• Use strong a source match range to thickness in plastic
• Note E||B, but protons starting from rest
Mylar Window
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
a Source
Heating (cooling) to equilibrium…
What do we expect?
He
1MV/m
.9MV/m
.8MV/m
.7MV/m
.6MV/m
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
• Vary gas
pressure/density
• Vary Efield strength
• Vary distance
• Measure energy directly
• Can our MC predict
equilibrium energies?
Efield coil
Support structures
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
Source holder
Assorted Insulating
Spacers & support
structures
Status of Experiment
• Cryostat & Magnet
commissioned
• Grid constructed &
tested. Maintained
98KV in vacuum
• Source & support
structures constructed
• Electronics &
detectors available
FWHM=250eV
• Silicon Drift Detector gives excellent resolution
• Thus far Fe55 X-rays
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
Summary
• Frictional Cooling is being persued as a potential cooling
method intended for Muon Colliders
• Simulations of mostly ideal circumstances show that the 6D
emittance benchmark of 1.7x10-10 (m)3 can be achieved &
surpassed
• Simulations have been supported by data from Nevis
Experiment & will be tested further at the Frictional Cooling
Demonstration to take place at MPI Munich
• Future investigations are also on the program:
• R&D into thin window or potential windowless systems
• Studies of gasbreakdown in high E,B fields
• Capture cross section measurements at m beams
Frictional Cooling is an exciting potential
alternative for the phase space reduction of
muon beams
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan