# Presentation: 064584

## US LARP

- Plans for Electron Cloud
- and Beam-Beam at LBNL
- Miguel A. Furman (LBNL)
- mafurman@lbl.gov
*US LARP AP&BC Mtg.*
*BNL, May 19-20, 2004*

## Some Input and Context

- Input from CERN people at ECLOUD04 (April 19-23) http://www.cern.ch/icfa-ecloud04
- G. Arduini, V. Baglin, J. M. Jiménez, D. Schulte, F. Zimmermann
- Meeting at LBNL, April 26
- A. Drees, U. Iriso, M. Furman
- CERN APC mtg. Minutes (March 19)
- Individual suggestions from FZ and GA

- ESGARD has approved CARE program, including:
- ELAN (CLIC and TESLA; D. Schulte)
- HEHIHB (SuperLHC and VLHC; F. Ruggiero):
- “**electron cloud... codes** need _**comparisons and benchmarking**_** by beam measurements** and are of **common interest** for high-luminosity hadron colliders and high-intensity synchrotrons...  ...establish a working infrastructure in Europe parallel to the proposed US-LARP programme, which has as objective to  _streamline R&D work_ in the 3 big national labs in the US with the additional benefit of contributing to LHC upgrade studies. A **parallel US-LARP and CARE approach** would facilitate further the important information flow and **worldwide collaboration** efforts.”

## Some Issues

- EC survives for a long time at SPS (~few s)
- e– flux at wall for dipole magnet ~3x simulations both warm and cold detectors
- Measured e– spectrum “could agree better with simulations”
- Old vs. new ECLOUD simulations show some discrepancies
- some comparisons with other codes carried out (after ECLOUD02)
- qualitative agreement, but differences not explained (for lack of dedicated effort)
- e– flux dependence on vac. chamber height: peaks at 80 mm (=max. achievable)
- Main “knobs”: bunch length, batch spacing, vac. chamber height, N
- should be plenty to constrain the model significantly
- need to constrain SEY model; devise experiment (ie., build-up and dissipation of the EC)
- revisit satellite bunch scheme

## Partial List of Electron Cloud Tasks

- Main goal: specify optimal LHC conditioning scenario
- Conditioning of cold surface at LHC likely to be very different from warm at SPS
- What to do if beam screen SEY does not condition as hoped
- First attempt at defining scenario (FY05 del.)
- RHIC cold measurements (suggested by “all” CERN people)
- Install CERN detector in a RHIC cold magnet (J. M. Jiménez, A. Drees) (FY05 del.)
- Measure  along batch (U. Iriso) (FY05 del.)
- Simulate ECE at RHIC, callibrate code(s), understand warm vs. cold EC
- UI to learn POSINST; go to LBNL, and/or MF to BNL (FY05+ del.)
- Understand conditioning process in cold sections vs. warm (FY05+ del.)
- Understand global parameter space (eg., EC density vs. a few parameters) (FY05+ del.)
- Understand physics of map simulation technique (FY05+ del.)

## List (contd.)

- SPS
- Devise experiment to be compared against upcoming SPS measurements to constrain SEY model
- eg., build-up and decay time of EC vs. N, sB and batch gap length (FY05 del.)
- Estimate EC build-up and decay in quads (SPS plans to install “sweeping” detector) (FY06+ del.)
- MF, UI and M. Pivi planning to participate in scrubbing SPS MDs (June 2004)
- Reproduce measured spectrum and spatial distribution (FY05 del.)
- Reproduce calorimeter results (FY05 del.)
- Understand POSINST-ECLOUD differences (FY05 del.) (suggested by FZ)
- Think about BTF measurements (requested by GA)
- Think about microwave transmission measurements of EC density (suggested by FZ)
- Measure ion desorption count and composition by ion bombardment (requested by JMJ: send one person to CERN for a year to do measurements)
- Better measurements for simulation input (requested by FZ, but might not happen)
- SEY at low energy (<20 eV); reproduce CERN data (Cimino-Collins)
- Photoelectric yield and photon reflectivity (cold vs. RT; B-field effect (?)) for actual sawtooth beam screen samples; resolve existing discrepancies (at ALS?)

## List (contd.)

- LHC
- CERN will install an ECE diagnostic bench in IR4 (J. M. Jiménez) similar to SPS.
- Simulate and predict! Good for LARP to play important role in this.

## SPS schedule 2004

- Scrubbing runs (weeks 24 & 26):
-   N=(0.3-1.3)x1011, min. , fixed z, 1-4 batches, sB=25 or 75 ns
- Some expected results:
-  max. N and fill pattern at 25 and 75 ns for given cooling rate
-  improve precision in measurement of conditioning efficiency for cold dipoles
-  measure heat load and partial pressures in COLDEX
-  EC build-up in quads
-  EC build-up in TiZrV-coated chamber before activation (use artificial seed electrons)

## More SPS MD details (from G. Arduini)

- SPS MD in week 27: beam stability, optimize the machine settings to get rid  of the last 10-20% in emittance blow-up in order to get the nominal parameters. Measurements with COLDEX and electron clould detectors and calorimeters.
- Weeks 29 and 31: coasts (with RF ON) of 1-2 LHC batches at SPS injection energy (p=26 GeV/c). Study the issues of long term emittance blow-up for the nominal LHC beam. Benchmark HEADTAIL or similar codes (which are predicting important emittance blow-up).
- Week 40: coast with 1-2 LHC batches (nominal intensity) at p=270 GeV/c for similar purposes as above.
- Week 45: not yet defined.

## Commissioning plans

- Plan for shifts during SPS 2004 run:
- Miguel Furman (week 26, TBC)
- Mauro Pivi (week 26, TBC)
- Ubaldo Iriso (week x, TBC)
- Andy Wolski (?)
- Marco Venturini (?)
- Andreas Adelmann (PSI; ?)
- Present and foreseen effort in the LARP Program Proposal (in FTEs):
-            FY04 (actual)             FY05           FY06
- BB                  x                         0.3                 0.2
- EC            0.23-x                       0.4                 2

## Beam-Beam Tasks (Str.-Str. Effects)

- Crossing angle & finite bunch length effects on “sweeping beam” LHC luminometer
- Use realistic LHC design parameters
- _Deliverable_: detector efficiency vs. integration time for a given magnitude of signal
- Long-time  growth
- So far, done 106 turns, single IP
- Dependence on N, M and (x,y)    (N=protons/bunch, M=macroparticle charge)
- _Deliverables_:
- Disentangle numerical from physical growth rates
- Emittance growth rate
- Quantify halo formation
- Think about str.-str. effects for wire compensation (?)
- Budget for FY05: 0.3 FTE (30% of Ji Qiang)

## Beam-Beam Tasks for FY06+ (TBC)

- More long-time behavior studies on  growth and haloes
- Effects from bunch length, crossing angle, PCs, multiple IPs, B-T-B variation
- Benchmark BEAMBEAM3D against CERN fast multipole code
- Improved understanding of RHIC observations (e.g., tune spectrum)
- Multiple IPs, phase adv. between IPs, ...
- Separated beams