# Presentation: 264486

## LARP Accelerator Systems  Accelerator Physics Task 1.4.1.5 LHC Electron Lenses         

*Vladimir Shiltsev** *

## Content

- LHC Electron Lenses – LARP CM10

- Task Sheet
- Budget
- Simulations
- Design/Construction Project
- Experimental studies
- Summary

## “LHC electron lens” Task Sheet

- LHC Electron Lenses – LARP CM10

- “LHC electron lens” Task Sheet

**Statement of work for FY08:**  ”..This task comprises three separate units: Numerical studies on compensation with an electron lens in the LHC, design considerations for the LHC EL, and relevant experiments in the Tevatron with TELs”
**FY08 Deliverables: **
-  Report on numerical studies of head-on BBC in the LHC
-  Report on general layout of the LEL
-  Report on beam-beam compensation studies in Tevatron
- We asked 250k$, got 165k$

## 1.4.1.5 Budget

- LHC Electron Lenses – LARP CM10

## LHC e-Lens Simul’s (A.Valishev)

- Simulation with LIFETRAC – weak-strong macroparticle code. 1E4 particles X 1E7 turns
- 6D maps and beams separations from MADX. 1st and 2nd order chromaticity, diffusion
- 1 Gaussian electron lens ~102m from IP1 with e-beam size matched to proton beam, acting as head-on tune spread compensator

- At =0.0075 (doubled beam intensity) non-luminous losses are reduced by 1⁄2
- At =0.01 (triple beam intensity) life time is improved by a factor of 4!

- Shiltsev

- LHC Electron Lenses – LARP CM10

## Status of RHIC e-Lens Studies (Y.Luo)

- LHC Electron Lenses – LARP CM10

## RHIC e-Lens Simulations

- LHC Electron Lenses – LARP CM10

- Challenges:
- #1 explain RHIC observed beam-beam lifetime
- #2 optimal partial compensation+optimal Qx,y

## e-Lens Simul Status SLAC (A.Kabel)

**'Plibb' tracking code** now handles official LHC lattice, agrees to 1e-7 w/MADX optics
- Needed to add elens, new magnet types, separate rings logic, parsing, scripting, new special cases for map calculation
- Elens is drift-kick, can be cut-off gaussian, flat-top, softened flat-top
- Case considered
- LHC, 7TeV, IP 1,2,5,8 + 4 nearest LR parasitics each, weak-strong
- N=1.05e11 and up
- Single elens @ -103m (beta crossing, sigma ~ 1mm), gaussian w/varying cutoff

**tracking results:** very unsubtle test case: 1.05e11 -> 1.75e11
- Substantial losses on some 1000 turns
- Mitigated by e-lens Ieff ~ 10Am
- Quantitative results forthcoming

- Shiltsev

- LHC Electron Lenses – LARP CM10

## LAUC: LHC e-lenses

- LHC Electron Lenses – LARP CM10

## LHC e-lens parameters

- LHC Electron Lenses – LARP CM10

## LHC e-lens cost estimates

- LHC Electron Lenses – LARP CM10

## Gaussian Gun (V.Kamerdzhiev)

***MEASURED ELECTRON BEAM PROFILE***

- Shiltsev

- LHC Electron Lenses – LARP CM10

## Experiments and studies

- LHC Electron Lenses – LARP CM10

- Beam-beam compensation studies in Tevatron
- Electron beam size effect on proton lifetime improvement
- Tevatron has not ran steadily and reliably till now, waiting
- Quantify Improvement vs e-current *R(J_e)*
- Induce and detect pbar tunespread reduction or proton tunespread broadening
- No diagnostics now - working on DTM (V.K.) in meantime
- Gaussian Gun has been built (~15k$)
- Can probably be installed later in FY08
- Lower in priority than #1 and gridded gun test in Tev
- Tev next shutdown in Spring 2009
- If gridded gun no good for operation  take one TEL out?

## Summary

- LHC Electron Lenses – LARP CM10

- 	1. e-Lens task is  on budget now, FNAL reporting system hiccups fixed 2. Experimental activities status:
- gaussian gun fabricated and ~tested (to be cont’d and finished in FY08)
- Tev beam studies possible  but not scheduled yet
- Hollow beam gun to be designed by EPAC
- planning for RHIC-lens is pending the simulations progress
- moving one of TELs to RHIC in 2009 – to be discussed
- 	3. Simulations status:
- LIFTRAC progress, LHC lifetime simulated  - shows significant improvement by TEL
- Simulations at SLAC – very early, but shows significant lifetime improvement by TEL, too
- Simulations at BNL – concentrated on RHIC, see effect on emm-growth, need more work
- 4. Next steps - to discuss today:
- install Gaussian-gun in Tevatron and see tunespread reduction/increase - ?
- boost simulations for LHC at BNL, SLAC and FNAL - bring results to the level good for  comparison - with a lot of investigation and post-work anticipated;
- compare RHIC beam-beam observations (lifetime, emm growth?) with simulations;
- should RHIC e-lens be a part of future strategy to make LHC lenses - ?

## Back up slides

- LHC Electron Lenses – LARP CM10

## Numerical Simulations

- LHC Electron Lenses – LARP CM10

- General Approach:
- show that beam-beam effects turn “bad” above certain intensity N_p/bunch
- either introduce wires or turn off log-range BB and see how much further increase possible
- Turn-on e-lenses and see improvement
- Indications of “bad” in simulations
- Dynamic aperture	   not  observable
- Beam lifetime    	   measurable
- Emittance growth     measurable
- Coherent stability     measurable

## Plans

- LHC Electron Lenses – LARP CM10

- Given the status of the codes and groups,  budget guidance and available resources we, most probably, will be able to accomplish the task in FY09
- In FY08 we can:
- Get LHC lattice and load it into all codes
- Scan tunes around nominal
- Scan chromaticity dependencies
- Observe “bad” b-b-effects vs N_p
- We will work in close contact with BBLR team

## Long Range Compensation

- LHC Electron Lenses – LARP CM10

- DC wire can do the job better
- simpler
- cheaper
- ... but only for reasonable beam-beam separations
-    (3...4...5? Sigma)
- But (!) Electron Lens can
- act as “electron wire” at ANY separation
- not infinite current! (enough for 2-4 parasitics)
- current variable bunch-by-bunch
- can compensate b-b-b tune spread in *XX *crossing with many parasitics (next slide)

## Bunch tunes for XY and XX

- LHC Electron Lenses – LARP CM10

- Bunch tunes for *XY* and *XX*

## Location in LHC – I (55 cm)

- LHC Electron Lenses – LARP CM10

- J.Johnstone
- LARP-doc-560

- D_x < 9 cm
- σ = 1.1 mm
- @ *β**=2300m*

## Resources

- LHC Electron Lenses – LARP CM10

- Fermilab:
- V.Kamerdzhiev and full time Engineer, 10% VS
- A.Valishev, Yu.Alexahin (part-time, theory & simulation support)
- Brookhaven:
- Y.Luo and his group to simulate and develop
- W.Fischer – management and operation support
- CERN:
- Excellent work by U.Dorda, hope for T.Pieloni
- Support/interest from FZ, JPK, OB