Accelerator Physics

U.S. LARP

Wolfram Fischer

LARP DOE Review 12 June 2006, FNAL 1

Accelerator Physics

Currently 3 Tasks:

1. Electron cloud studies 2. Interaction region upgrade and beam-beam 3. Long-range beam-beam compensation

FY06 Budget: $670k

(31% BNL, 34% FNAL, 34% LBNL) Wolfram Fischer 2

1. Electron cloud studies (1) Leader: M. Furman, LBNL

Current work:

1. Optimal conditioning scenarios  Under way 2. Cross-check of CERN e-cloud calculations  POSINST vs. ECLOUD for heat load calculation 3. Support for analysis of experimental data  SPS, RHIC, future LHC pilot diagnostic bench 4. Open questions in e-cloud understanding  3D effects, ions, emittance growth FY06 Budget: $200k (25% BNL, 75% LBNL) Wolfram Fischer 3

1. Electron cloud studies (2) – recent activities

• • • Completed updated simulations of e-cloud power deposition in LHC dipoles – – M. Furman and V. Chaplin, PRST-AB

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, 034403 (March 20, 2006) • Tedious exploration of parameter space with 2D code POSINST (see below) Peak SEY d max now constrained to be <~1.2 for nominal intensity & bunch spacing – Code improvements 3D self-consistent code (WARP/POSINST) – – – – Jean-Luc Vay (LBNL) now 20% LARP funded (starting FY06) Initial qualitative results for one bunch in one FODO cell (LARP mtg, Apr. 05) New results for a train of 5 bunches with more detailed model (see below) Code improvements RHIC studies – Feb. 2006: two CERN e – important) • detectors installed (some not LARP funded, but Common pipe region in IP10, warm section – – Polarized proton beams for this run Ping He doing RHIC simulations; calibration barely started Wolfram Fischer 4

1. Electron cloud studies (3) – Simulation: ecloud at LHC dipoles ( Furman and Chaplin, PRST-AB

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, 034403)

ecloud power deposition – – – – POSINST code

dP dz

LHC arc dipole magnet key parameters: N b , t b , d max current result: d max must be <1.2-1.3

• achievable but not easy t b =25 ns t b =25 ns N b =1e11 t b =75 ns

1.15e11

: cooling capacity available for EC power deposition

Wolfram Fischer 5

1. Electron cloud studies (4) – 3D self-consistent simulations (WARP/POSINST) ( courtesy J.-L. Vay)

•LHC FODO cell • can now follow batch of bunches with photo- e – and • Benchmark code against HCX experiment (LBNL) • expt. and sim. agree quantitatively secondary e – on characteristics of e – oscillations • snapshot from run with 5 observed in magnetic quadrupole bunches: flooded with electrons: WARP/POSINST-3D T = 0.3

 s WARP/POSINST-3D T = 4.65

 s

Electrons bunching

Wolfram Fischer experiment simulation

Oscillations Beam ions hit end plate

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Sec 9

1. Electron cloud studies (5) – LHC type e-detector in RHIC (M. Jimenez, A. Drees, D. Hseuh, P. He)

Phobos magnet TWC Warm Dipoles Electron Detector Sec 10 IP Wolfram Fischer Existing concrete stands 5m • • • • • study e-cloud formation with and w/o dipole field much higher sensitivity than the RHIC type detectors focus on surviving electrons in gaps and fill pattern optimization approved for APEX time during this run in FY06 (polarized protons) collaboration BNL (A. Drees, D. Hseuh et al. ) and CERN (M. Jimenez et al.) 7

1. Electron cloud studies (6) – Future plans

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Heat load calculations for 12.5ns bunch spacing (new and urgent request) Estimate of scrubbing time 3-D simulations including ion effects (Is 2-D enough? Gap survival? Ion effects?) Emittance growth from electron clouds (recent thesis by E. Benedetto, CERN) Analysis of SPS data Simulate “pilot diagnostic bench” Support CERN detector at RHIC Wolfram Fischer 8

2. Interaction region and beam-beam (1) Leader: T.Sen, FNAL

Current work:

1. Interaction region optics design for upgrade 2. Energy deposition for upgrades 3. Beam-beam simulations for upgrades

FY06 Budget: $260k

(69% FNAL, 31% LBNL) Wolfram Fischer 9

2. Interaction region upgrade and beam-beam (2)

Current investigations focus on 3 scenarios 1.

2.

3.

Quadrupole first Dipole first with round beam Dipole first with flat beams Proposed CERN rating (F. Ruggiero) 1.

Luminosity reach (complex) 2.

3.

Estimated R&D time T R&D (years) Estimated commissioning time T OP (years) October 2006: CARE HHH Workshop “Towards a roadmap for the upgrade of the LHC and GSI”, Valencia Wolfram Fischer 10

2. Interaction region upgrade and beam-beam (3)

Like 1 st generation IR Like RHIC IR + Q close to IP - LR beam-beam Wolfram Fischer + fewer LR beam-beam - Q further away from IP 11

2. Interaction region upgrade and beam-beam (4) IR Magnet apertures and fields

Pole tip field [T] Quads 1 st Dipoles 1 st : triplets Dipoles 1 st : doublets 10 11 10 Aperture [mm] 101 107 104

Energy Deposition

Major issue in all optics, but dipole designs more challenging.

Beam-beam interactions

Demonstration of wire compensation would favor quads 1 st .

Chromaticity and Nonlinear Correctors

Corrector strengths lower with quads 1 st but independent control of 2 beams with dipoles 1 st .

Luminosity gain with lower L*

Larger gain with quads 1 st .

Flux jumps in IR magnets

Chromaticity jumps small (~2 units) with Δb 3 = 1 in both optics if spurious dispersion in IR is controlled to ~1cm at IP. Nonlinear effects need to be studied Wolfram Fischer 12

2. Interaction region upgrade and beam-beam (5)

Summary by J. Johnstone Wolfram Fischer 13

2. Interaction region upgrade and beam-beam (6)

Summary by J. Johnstone Wolfram Fischer 14

2. Interaction region upgrade and beam-beam (7) – Summary

• • • • • IR optics layouts have been proposed, with a lattice repository at CERN LARP work on 3 layouts: – – Quadrupole first Dipole first & round beams – Dipole first & flat beams Detailed energy deposition study for quad first Goal is to define baseline scenario by end of 2006 (Valencia workshop), challenging Some details not yet evaluated – – Long-range beam-beam Tolerance to errors Wolfram Fischer 15

2. Interaction region upgrade and beam-beam (8) – Future

Continue in current areas:

1. Interaction region optics design for upgrade 2. Energy deposition for upgrades 3. Beam-beam simulations for upgrades

New area:

1. Study electron lenses for head-on beam-beam compensation (simulations only next year to determine tolerances to e-beam parameters) Wolfram Fischer 16

3. Long-range beam-beam compensation (1) Leader: T. Sen FNAL

Current work:

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2.

3.

4.

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Define long-range experiment at RHIC (FY05/06) Construct 2 RHIC long-range compensators (FY06) Simulate long-range compensation (FY06) Test long-range compensation with beam (FY07) Test pulsed compensator operation (FY08) FY06 Budget: $210k (76% BNL, 24% FNAL) - $160k for construction + RHIC support (construction labor costs, experimental program) Wolfram Fischer 17

3. Long-range beam-beam compensation (2)

• LRBB important effect in LHC, possibly eRHIC • With >120 bunches cannot avoid long-range beam-beam interactions (eRHIC) • RHIC is a good test bed for a wire compensator (more difficult in Tevatron) 52.4 ns 45.0 ns 32.7 ns 15.7 m 13.5 m 9.8 m DX IP BPM (x,y) 5.1 ns bunch length 1.52 m Long-range interactions with 360 bunches BPM (x,y) Long-range interactions with 180 bunches DX Wolfram Fischer 18

3. Long-range beam-beam compensation (3)

long-rang interaction (vertical) long-range compensation (up) Df x,y = 6 deg ( b * = 1m)

RHIC Sector 5 bi5 IP6 yo5

Wolfram Fischer long-range compensation (down)

Because of phase advances, can only properly compensate a single long-range interaction per turn.



Demonstrate measurable effect.

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3. Long-range beam-beam compensation (4) Beam loss rates as a function of vertical separation, conditions close to those needed for compensation 100 GeV - Not easy to create good observable

Wolfram Fischer 20

3. Long-range beam-beam compensation (5)

Wire compensator under construction at BNL • 1 unit in each ring, side-by-side • vertically movable (wire in shadow of adjacent beam pipe when not in use) • up to 125Am strength (like LHC), need only 4Am for RHIC Wolfram Fischer 21

3. Long-range beam-beam compensation (6) Beam-beam simulations of 2006 experiments

Motivation: Tests and improvements of codes, predictions of observations in 2006 and of wire compensation Four groups FNAL: V. Ranjbar, T. Sen; SLAC: A. Kabel; LBL: J. Qiang; University of Kansas: J. Shi Website: http://www-ap.fnal.gov/~tsen/RHIC for information exchange and results Wolfram Fischer 22

3. Long-range beam-beam compensation (7) Kansas

No sextupoles Relative Lifetime Emittance growth

LBL FNAL SLAC

Losses BBSIM (VR, TS) simulations for lifetime show

a linear dependence on separation

Wolfram Fischer 23

3. Long-range beam-beam compensation (8)

LHC would need modulated compensator strength From U. Dorda, F. Zimmermann • •

Pulsed PS may be built at CERN, could be tested at RHIC Technically very challenging

•

Should also evaluate benefits with DC excitation only

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3. Long-range beam-beam compensation (9) – Future plans

1.

Finish construction, install compensators in RHIC 2.

Test compensator effect with single beam 3.

Test long-range compensation 4.

Simulation studies to determine best wire parameters and effectiveness of compensation Wolfram Fischer 25

4. New Task for FY07 – Feasibility of new initiatives V. Shiltsev

Goal: evaluate feasibility of new proposals before they become a full task Proposals under consideration:

• Fiberoptic-based synchrotron radiation diagnostic • Crab cavities for IR upgrade • Low energy ring LHC injector (LER)

All studies are to result in a report, no hardware effort at this stage.

Wolfram Fischer 26

LARP AP – Summary

Currently 3 Tasks:

1. Electron cloud studies 2. Interaction region upgrade and beam-beam 3. Long-range beam-beam compensation

Plan to have new task next year

4. Feasibility of new initiatives Wolfram Fischer 27