# Presentation: 064595

## The Center for Beam PhysicsTheory Group

- Miguel Furman
- Theory Group Leader
- DOE HEP Program Review
- LBNL, 18-19 February, 2004

## CBP Theory Group

- Carry out original research in accelerator design and beam dynamics.
- Provide accelerator physics support for existing or future accelerators.
- Explore new mechanisms for particle acceleration and related issues.

- Our research is strongly “customer-driven”
- by present or future machine performance issues at LBNL and elsewhere

## Staff and Funding

- Staff
- M. Furman (group leader)
- W. Fawley
- G. Penn
- M. Venturini
- A. Sessler (emeritus)
- A. Wolski
- J. Wurtele (UCB faculty)
- M. Xie
- A. Zholents
- M. Zolotorev
- funding from HEP base: 4 FTEs
- funding from NLC: 2 FTEs
- balance: LDRDs, DARPA, IPP, LARP, DAHRT, LCLS

- Post doc
- M. S. Hur (Wurtele)
- Grad students (Wurtele)
- A. Charman
- V. Gorgadze
- R. Lindberg
- F. Peinetti (U. Turin)
- Undergrads (UCB)
- J. Rembaum (Wurtele)
- D. Bates (Wolski)
- Researcher (Wurtele)
- M. Reinsch
- Guest scientists (sporadic)
- M. Pivi (SLAC)
- R. Palmer (BNL)

## HEP-Related Activities

- Lattice design and beam dynamics for NLC damping rings.
- Support PEP-II performance improvement.
- Electron-cloud effect.
- Beam-beam interaction (with AMAC group).
- Optical stochastic cooling (test at BNL).
- Novel acceleration mechanisms.
- Laser-pulse amplification.

## NLC Damping Rings

- LBNL has responsibility for design NLC DRs.
-  work in collaboration with SLAC and KEK.
- Basic requirement: low emittance beams and fast rep rate.
- lattice design: provide dynamical stability in the presence of:
- strongly nonlinear fields (wigglers)
- ground motion
- magnet alignment
- correction of coupling and vertical dispersion
- Collective effects.
- improved wiggler magnet modeling and analysis
- electron cloud effect
- intra-beam scattering
- impedance effects
- fast beam-ion instability

- (details in Andy Wolski’s talk)

## Improvement of PEP-II Performance

- Goal: increase *L* to 2x1034 cm–2s–1 by summer 2006 (i.e., factor ~3 from now)
- Modeling techniques (measure closed-orbit response to parameter changes)
- developed at SSRL and successfully applied at ALS
- Improved model of the interaction region
- Proposals to reduce momentum compaction factor 
- goal: decrease bunch length
- work in collaboration with C. Steier (ALS)

- (details in Andy Wolski’s talk)

## Electron Cloud Effect (ECE)

- Unwanted electrons perturb the beam.
- surface physics effect compounded by beam structure and intensity
- first manifestation: beam-induced multipacting (ISR, 1977)
- seen at PF, PEP-II, KEKB, BEPC, PS, SPS, APS(e+), PSR, RHIC
- expected at LHC, SNS, NLC DRs
- possible consequences: instability, emittance dilution, vacuum pressure rise, interference with diagnostic instrumentation, excessive power deposition
- we are an early pioneer in the field of ECE simulations and analysis
- Our main focus:
- simulations for LHC, SPS, and NLC damping rings
- identify important ingredients; mitigating mechanisms
- code calibration: APS, PSR and SPS (lots of dedicated measurements)
- LBNL is the main organizer of the ECLOUD04 ICFA workshop
- Napa, April 19-23, 2004
- co-sponsored by ICFA, LBNL, CERN, ORNL and SNS
- _[http://www.cern.ch/icfa-ecloud04 ](http://www.cern.ch/icfa-ecloud04)_

## Electron Cloud Simulations for LHC

- Main issue: power deposition on vacuum chamber.
- could overwhelm the cryogenics system if not mitigated
- main goal: detailed understanding of effects from the secondary electron emission process off the vacuum chamber surfaces
- work in close contact with LHC personnel (LHC Vacuum Group and AP)
- simulation benchmarking against measurements at SPS
- the ECE is a possible _performance-limiting issue_
- Current conclusion:
- power deposition is sensitive to details of the secondary e– emission process
- not completely understood
- more work is critically needed:
- improved simulations
- better input data for the simulations

## Example: Sensitivity to Details of Secondary Emission

- Simulated power deposition (W/m) vs. time in an LHC arc dipole
- (for peak SEY=2.05, on the “pessimistic” side)

**e+**r = 10%

**e+**r = 0

**e+**r = 43%

- beam current (A.U.)

- Detailed view for 1.02 < t < 1.06 s

## Example: Code Calibration at the PSR

- slope = 200 ns

- data: Macek & Browman
- PAC03 paper RPPB035

- simulation

- conclusion: **(0)≈0.4-0.5, consistent with bench measurements

- electron line density

- beam line density

## ECE: Collaborations and Knowledge Transfer

- Collaboration with HIF group at LBNL
- combine strengths of two simulation codes
- lead to self-consistent simulations
- LDRD supported (FY04 is 2nd year out of 3)
- improved tools will be valuable to all HEP and non-HEP intense beams (such as HIF drivers)
- in partnership with LLNL
- experimental part, also LDRD-supported
- Collaboration with Tech-X Corp.
- supported by an SBIR phase 2
- wrapped Python code around main secondary emission modules we developed
- modular, easy to plug into your own code
- state of the art simulations
- will prove valuable for RF multipactor simulations
- ready for general distribution!

## Other Activities  

- Beam-beam interaction simulations (LHC, Tevatron, PEP-II).
- applied early on to PEP-II design (issues: asymmetry, parasitic collisions)
- LHC performance (LBNL sweeping luminosity detector)  (Rob Ryne’s talk)
- Optical stochastic cooling.
- higher bandwidth than microwave stochastic cooling, hence faster cooling rate
- Invention and design of longitudinal beam profile monitor  (John Byrd’s talk)
- will be installed in LHC
- tested at the ALS
- Novel acceleration mechanisms
- plasma inverse transition acceleration (inverse of EM transition radiation)
- rigorous, general theory relating radiation and acceleration
- Laser-pulse amplification (Raman backscatter amplifier).
- increase laser pulse peak field without large-scale optics by means of plasmas
- potential applications to laser-particle acceleration
- Applications of quantum computers.
- if a QC is built, can one use it for *classical* physics calculations (e.g., fast particle tracking)?

## Conclusions

- Accelerator physics theory is essential to understand performance limitations in present and future intense-beam accelerators
- machine *must* perform at the level desired by experimentalists
- in particular, HEP colliders
- issues: beam-beam effect, electron-cloud, collective instabilities, ...
- Our group is dedicated to solving these problems.
- We have strong collaborations with other labs/projects.
- However...
- our HEP work is leveraged by other funding (e.g., LDRDs)
- to maintain our productivity, we need to
- increase student participation
- increase post-docs from 1 to 2, and maintain this level