1. Tom Roberts Muons, Inc. Illinois Institute of Technology
Simulation Issues - and - MICE Interim Report on MANX after MICE (Two talks for the price of one.)
Tom Roberts
Muons, Inc.
Illinois Institute of Technology
February 4, TJR
Simulation Issues / MANX After MICE

2. Simulation Issues
As author of one of the primary simulation programs used in current muon collider design studies, I am keenly aware of some of the limitations of current simulation codes.
And I am surely blind to others!
As an example, extrapolating from current measurements of energy loss and multiple scattering to a full cooling channel has a ratio comparable to extrapolating from a rifle to 0.1 c.
Clearly some humility is needed!
Or rather, some EXPERIMENTS are needed…
February 4, TJR
Simulation Issues / MANX After MICE

3. Simulation Issues / MANX After MICE
All programs are prone to “garbage in, garbage out” Complex simulation programs are even more prone to this − This is old hat and I won’t discuss it
Simulation programs make many approximations − This is old hat and I won’t discuss it
Simulation programs have many parameters to select − This is old hat and I won’t discuss it
Simulation programs require enormous CPU resources − This is old hat and I won’t discuss it
Real systems are very complex and difficult to represent in a simulation program − This is old hat and I won’t discuss it
Etc….
February 4, TJR
Simulation Issues / MANX After MICE

4. Simulation Issues / MANX After MICE
Existing programs do not implement all relevant physics phenomena − This is worth a discussion
Electromagnetic processes – the essence of muon cooling
Accurate multiple scattering models (tails become important…)
Accurate energy straggling model
Correlation between multiple scattering and energy loss
Effect of magnetic field on multiple scattering
Thick vs. thin absorbers
Realistic 3-d EM fields (e.g. waveguide ports, HOM correctors, …)
February 4, TJR
Simulation Issues / MANX After MICE

5. Simulation Issues / MANX After MICE
Collective processes (vacuum)
space charge  in progress
wake fields
coherent synchrotron radiation
beam-beam interactions
electron cloud effects
Collective processes (in matter)  starting
space charge screening by material
bunch-induced polarization of material causing intensity-dependent energy loss and instability
effects of matter on wake fields
coherent bremstrahlung
for all the above, consider dependency on material properties, head-tail differences, and bunch-to-bunch effects (i.e. time dependence)
February 4, TJR
Simulation Issues / MANX After MICE

6. Simulation Issues Decays and Interactions in macroparticle models
Polarized muon processes
Normalization uncertainties
Pion production models
Distortions of mercury target
In short, there are many known physics processes not implemented in current simulation programs. Some are surely important for muon collider design.
Many of them have never been measured.
Measuring EM processes in a thick absorber is a good start.
February 4, TJR
Simulation Issues / MANX After MICE

7. MICE Interim Report on MANX After MICE Tom Roberts, IIT
“The MICE collaboration members generally strongly support the idea of a follow-up experimental program in ionization cooling studies. […] The concept of helical cooling channel seems very promising and the synergy with muon colliders is exciting.” − Alain Blondel, MICE Spokesperson
This is a summary of a report presented by Malcolm Ellis at the recent MICE Collaboration Meeting (Jan. 14, Harbin, China). Prepared by:
John Cobb (chair), Chris Rogers, Malcolm Ellis, Yoshi Kuno
February 4, TJR
Simulation Issues / MANX After MICE

8. Simulation Issues / MANX After MICE
MICE has convened a committee to consider follow-on possibilities; MANX is by far the most advanced, and the only one considered at this time
The questions suggested by the MICE Executive Board:
Space-consistency in the MICE hall
Scope and adequacy of proposals in view of existing
MICE instrumentation, and
Infrastructure
Consistency of time scales
Comment on resources available from MANX and MICE
Good use of MICE infrastructure resources
February 4, TJR
Simulation Issues / MANX After MICE

9. Simulation Issues / MANX After MICE
MANX proposal assumes much of MICE will exist
MICE is a collaboration
Infrastructure is not (yet) a facility
Operated by MICE collaborators
Instrumentation is not owned ‘in common’ by MICE
Individual owners of instrumentation may have own preferences or funding agency constraints
‘MICE’ itself cannot agree to support any new initiative – a new collaboration would be needed
MANX – or any new cooling experiment – at RAL would probably require substantial UK involvement
RAL is small part of MICE
Not same relationship to users as CERN or Fermilab
February 4, TJR
Simulation Issues / MANX After MICE

10. Simulation Issues / MANX After MICE
Two possible configurations:
MANX with matching
Off-Axis MANX – reduces cost of the magnet
350 MeV/c  150 MeV/c
New fiber tracker planes inside matching and HCC
New high-resolution TOF counters (<5 psec resolution)
Being developed
February 4, TJR
Simulation Issues / MANX After MICE

11. Simulation Issues / MANX After MICE
Off-Axis MANX
The MICE committee did not consider the off-axis configuration of MANX, believing the spectrometer solenoids had not been designed to handle off-axis forces
This is not actually a show-stopper:
“The cold mass support system for the spectrometer solenoid is quite robust. […] I think that the supports can carry 200 kN in the radial direction while carrying 450 kN in the axial direction.” − Mike Green
Of course the overall system must be properly engineered, including quench forces
The off-axis configuration puts the downstream spectrometer closer to the iron magnetic shield wall, which must be considered (forces, field distortions, infrastructure)
February 4, TJR
Simulation Issues / MANX After MICE

12. MANX After MICE Conclusions – I
MANX with matching fits in the MICE hall
Off-Axis MANX should also fit
effects of the magnetic shield wall?
MICE spectrometers appear more than adequate for transverse planes
Large volume of LHe needs new infrastructure; ditto for LH2
Placement of new TOF counters needs to be considered
The down-stream PID detectors may be too small, if the downstream TOFs need additional space
February 4, TJR
Simulation Issues / MANX After MICE

13. MANX After MICE Conclusions – II
350 MeV/c is within the magnet capabilities of the beamline
Higher pi/mu ratio at 350 MeV/c makes particle ID important
MICE Cherenkov counters may be inadequate
Investigating – can probably be made to work
TOF1-TOF0 give ~7 sigma separation for pi/mu at 350 MeV/c
Also: larger absorber means higher pi/mu ratio may be OK
Matching from spectrometer to HCC at 350 MeV/c probably cannot be done with the current design
Needs to be considered in the MANX magnet design
Perhaps reducing initial momentum to 240 MeV/c reduces or eliminates the problems with 350 MeV/c
February 4, TJR
Simulation Issues / MANX After MICE

14. MANX After MICE Conclusions – III
Timescale to follow MICE in 2013 seems rather optimistic
Need selection of configuration
Need engineering of HCC itself and in MICE hall
Need to construct the HCC magnet
Need simulations of performance, resolutions, etc.
Need high-resolution TOF development
Resources are very tight
February 4, TJR
Simulation Issues / MANX After MICE

15. MANX After MICE Conclusions – IV
MICE is not a facility, and MICE as a collaboration cannot commit to a follow-on experiment
A new collaboration is required
All groups must agree on a program & apply for new funding
Within the MICE collaboration, there is qualified support for MANX (and for other potential follow-on experiments)
The MICE committee believes that STFC would most likely support a new initiative
No show-stoppers have been found.
February 4, TJR
Simulation Issues / MANX After MICE

16. Simulation Issues / MANX After MICE
“The MICE collaboration members generally strongly support the idea of a follow-up experimental program in ionization cooling studies. […] The concept of helical cooling channel seems very promising and the synergy with muon colliders is exciting.” − Alain Blondel, MICE Spokesperson
February 4, TJR
Simulation Issues / MANX After MICE