Frictional Cooling Frictional Cooling Studies at Columbia University/Nevis Labs Studies at Columbia University/Nevis Labs Raphael Galea, Allen Caldwell Raphael Galea, Allen Caldwell + Stefan Schlenstedt (DESY/Zeuthen) Stefan Schlenstedt (DESY/Zeuthen) Halina Abramowitz (Tel Aviv University) Halina Abramowitz (Tel Aviv University) Summer Students: Emily Alden Summer Students: Emily Alden Christos Georgi Christos Georgi Daniel Greenwald Daniel Greenwald Laura Newburgh Laura Newburgh Yujin Ning Yujin Ning Will Serber Will Serber Inna Shpiro Inna Shpiro How to reduce beam Emmittance by 10 6 ? 6D,N = 1.7 10 -10 (m) 3
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Frictional CoolingFrictional Cooling
Studies at Columbia University/Nevis LabsStudies at Columbia University/Nevis Labs
Raphael Galea, Allen CaldwellRaphael Galea, Allen Caldwell
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Stefan Schlenstedt (DESY/Zeuthen)Stefan Schlenstedt (DESY/Zeuthen)
In 1 d=10cm*sqrt{T(eV)} keep d small at low T reaccelerate quickly
Cooling cells
Phase rotation sections
Not to scale !!
He gas is used for +, H2 for -. There is a nearly uniform 5T Bz field everywhere, and Ex =5 MeV/m in gas cell region Electronic energy loss treated as continuous, individual nuclear scattering taken into account since these yield large angles.
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).
•Incorporate scattering cross sections into the cooling program
•Born Approx. for T>2KeV•Classical Scattering T<2KeV
•Include - capture cross section using calculations of Cohen (Phys. Rev. A. Vol 62 022512-1)
•Difference in + & - energy loss rates at dE/dx peak•Due to extra processes charge exchange•Barkas Effect parameterized data from Agnello et. al. (Phys. Rev. Lett. 74 (1995) 371)
•Only used for the electronic part of dE/dx
Yields & Emittance
Look at muons coming out of 11m cooling cell region after initial reacceleration.
Yield: approx 0.002 per 2GeV proton after cooling cell.Need to improve yield by factor 3 or more.
Emittance: rms x = 0.015 m y = 0.036 m z = 30 m ( actually ct)
Px = 0.18 MeVPy = 0.18 MeVPz = 4.0 MeV
6D,N = 5.7 10-11 (m)3 6D,N = 1.7 10-10 (m )3
Problems/Things to investigate…
• Extraction of s through window in gas cell •Must be very thin to pass low energy s•Must be reasonably gas tight
• Can we apply high electric fields in gas cell without breakdown (large number of free electrons, ions) ? Plasma generation screening of field. • Reacceleration & bunch compression for injection into storage ring• The capture cross section depends very sensitively on kinetic energy & falls off sharply for kinetic energies greater than e- binding energy. NO DATA – simulations use theoretical calculation• +…
RAdiological Research Accelerator FacilityPerform TOF measurements with
protons2 detectors START/STOPThin entrance/exit windows for a gas cellSome density of He gasElectric field to establish equilibrium energyNO B field so low acceptance
Look for a bunching in time Can we cool protons?
4 MeV p
Contains 20nm window
Proton beam
Gas cell
Accelerating grid
Vacuum chamber
To MCP
Si detector
Initial conclusions: no obvious cooling peak, but very low acceptance due to lack of magnetic field. Use data to tune simulations. Redo experiment with a solenoidal magnetic field.
Lab situated at MPI-WHI inMunich
Future Plans
• Frictional cooling tests at MPI with 5T Solenoid, source• Study gas breakdown in high E,B fields• R&D on thin windows• Beam tests with muons to measure capture cross section
-+H H+ e+’smuon initially captured in high n orbit, then cascades down to n=1. Transition n=2n=1 releases 2.2 KeV x-ray.
Si drift detectorDeveloped my MPIHLL
Summary of Frictional Cooling
Nevis Labs work on - capture
MPI lab for additional questions
•Works below the Ionization Peak•Possibility to capture both signs•Cooling factors O(106) or more? •Still unanswered questions being worked on but work is encouraging.
Frictional Cooling: stop the
Start with low initial muon momenta
High energy ’s travel a long distance to stop High energy ’s take a long time to stop
Motion in Transverse Plane
€
rE
€
rB
Lorentz angle
€
rF = q(
r E +
r v ×
r B ) −
dT
dxˆ r
•Assuming Ex=constant
Simulations Improvements
•Incorporate scattering cross sections into the cooling program
•Born Approx. for T>2KeV•Classical Scattering T<2KeV
•Include - capture cross section using calculations of Cohen (Phys. Rev. A. Vol 62 022512-1)
Scattering Cross Sections
•Scan impact parameter (b) to get d/d from which one can get mean free
•Difference in + & - energy loss rates at dE/dx peak•Due to extra processes charge exchange•Barkas Effect parameterized data from Agnello et. al. (Phys. Rev. Lett. 74 (1995) 371)
•Only used for the electronic part of dE/dx
Target Study
Cu & W, Ep=2GeV, target 0.5cm thick
Target System
cool + & - at the same time calculated new symmetric magnet with gap for target
Target & Drift Optimize yield
Maximize drift length for yield Some ’s lost in Magnet aperture
Phase Rotation
First attempt simple form Vary t1,t2 & Emax for maximum low energy yield