ILCDR08 Report - Electron Cloud Session -. 2008.07.08 – 11 @Cornell Univ. Y. Suetsugu, KEK. Electron Cloud Group Charge (M. Palmer).
2008.07.08 – 11 @Cornell Univ.
Y. Suetsugu, KEK
Electron Cloud Group Charge(M. Palmer)
The charge to the Electron Cloud working group is to review the status of electron cloud simulations, both for electron cloud growth and for electron cloud induced beam dynamics, the benchmarking of the major codes against each other, and benchmarking of the codes against experiment. The group should also review the status of electron cloud measurement and mitigation techniques. Finally, the group should look at the world-wide experimental program and inputs that are required for the ILC and CLIC damping ring designs, paying particular attention to identifying tests that are needed as part of the CesrTA program.
This charge is quite ambitious; we made headway, but continuing discussions and real work will be required to fulfill the charge
RFA type electron detectors with Faraday cup or MCP or multi-strip anode are installed to KEKB LER.
Comparison between Cornell-type thin RFA and APS-type
Almost consistent each other
Newly developed RFA for
Dipole Chamber RFA
Electron density can be estimated by measuring the phase shift of transmitting microwave
for CESR-TA, following PEP-II
Effects on Beam (Flanagan)
Tune shift measurement using witness bunch
Use long trains e+/e- bunches to generate a electron cloud density.
Place witness bunches
at varying times after
the generating train
and measure the
coherent tune shift
of the witness bunch.
Thin RFA is prepared for wiggler section (B-magnet)
Microwave transmitting method with better hardware
Measurement in Q-magnet or in solenoid field: Future issues
Effect on beam
Measurement of coherent instabilities, incoherent emittance growth
Beam size: Development of X-ray beam size monitor
Provide valuable data for verification of simulation codes.
All but the last talk are about “build-up ecloud physics”
M. Pivi et al, SLAC
Electron cloud signal in stainless steel chamber.
Electron cloud signal in two smooth (flat) TiN-chambers and two grooved TiN-chambers installed in PEP-II.
Preliminary table to be completed as input for Technical Design Phase. Goal is to turn all Red colors to Green in the next two years.
Other mitigations under development! (ex: Carbon coating CERN)
Y. Suetsugu, H. Fukuma, KEK
M. Pivi and W. Lanfa, SLAC
Experimental Plan at KEKB Positron RingGrooved Surface, and Clearing Electrode Ver.2
B = 0.75 T
Test chamber with antechambers
Use the same location
Plan of measuring cloud density in the solenoid field and in the quadrupole field
K. Kanazawa (KEK)
Electrons accelerated by a bunch along X-axis reach the detector.
-What experiments will best pin down the SEY model parameters, particularly the number of rediffused electrons? The photoelectron generation model parameters?
-How can we test that the effects of the “pinch” are being properly modeled?
-How can we best establish confidence in the instability predictions? The predictions for emittance growth?
-What additional experiments are needed to establish high confidence in the proposed mitigation techniques to be used in the ILC damping ring?
Cesr TA: A superb and ambitious e-cloud R&D program
Essential resources are in place
Diagnostics and simulation tools
Knowledge, flexibility and maturity of the machine
e+ / e–, almost arbitrary fill pattern,…
Knowledge of certain relevant e-cloud parameters
Dedicated beam time
Close collaboration with outside experts is highly desirable to make rapid and sustained progress
I have a suspicion that 2 years will not be enough to achieve all the desired goals
Nevertheless, I am quite confident of a large degree of success, both for Cesr TA in particular, and for the e-cloud field in general.