LHC-CC10, 4th LHC Crab Cavity Workshop

15 Dec 2010, 08:30 → 17 Dec 2010, 18:30 Europe/Zurich

6/2-024 - BE Auditorium Meyrin (CERN)

Frank Zimmermann (AB/ABP), Rama Calaga (BNL), Rogelio Tomas (CERN)

Workshop Charge:

1. Can compact cavities for the LHC be realized and made robust with the complex damping schemes ?

2. Are crab cavities compatible with LHC machine protection, or can they be made to be so ?

3. Should a KEKB crab cavity be installed in the SPS for test purposes ?

LHC-CC10 Summary Report http://cdsweb.cern.ch/record/1338530/files/EuCARD-REP-2011-001.pdf

Project Document Draft Project_description_20-Aug_v3.docx Project_description_20-Aug_v3.pdf

Wednesday, 15 December

08:30 → 10:10 LHC-CC status & review

08:30 Welcome & Workshop Overview

Speaker: Steve Myers (CERN)

08:40 KEK-B Achievements & Crabs

The implementation of large angle crab crossing using superconducting cavities operating on the TM110 mode. Beam commissioning, operation, cavity availability, reliability and luminosity increase from the crab crossing (purely geometric gain plus gain in beam-beam tune shift). KEKB crab-cavity diagnostics and set-up/tuning/alignment procedures. Frequency, reasons, beam observations, and possible mitigation of crab-cavity trips. Aperture issues. Ramping and leveling. KEKB upgrade plan without crab cavities and the reasons.

Speaker: Yoshihiro Funakoshi (KEK)

Slides Funakoshi_LHC_CC10.pdf Funakoshi_LHC_CC10.ppt

09:00 LHC luminosity achievements & limitations

LHC beams and luminosity evolution during the 2010 Run with some estimates on future projections. Present intensity limitations from operational experience and machine availability. Hints on upgrade beam parameters based on LHC experience (for example, lower emittance and higher than nominal beam-beam tune shift)

Speaker: Oliver Bruning (CERN)

Slides LHC_luminosity_achievements_&_limitations.pdf LHC_luminosity_achievements_&_limitations.ppt

09:20 Perspective from the Experiments

Detector upgrade plans and schedule for the experiments, and their alignment with planned LHC upgrade. Constraints and requirements from the experiments on the proposed upgrade scenarios with crab cavities, early separation with D0 dipole, and large Piwinski angle scheme. Planned civil engineering and upgrade work around IP's 1 and 5 that could have synergies or conflicts with a crab-cavity installation.

Speaker: Dr Jordan Nash (Imperial College)

Slides JN_CRABWS_DEC_2010.pdf JN_CRABWS_DEC_2010.ppt

09:40 HL-LHC Design Study & Crab Cavities

The motivation of the high luminosity LHC design study, goal, scope, required technologies, time line, technology choices and decision dates, overall cost estimate and resources. The collaborative framework of this design study with EuCARD, US and Japanese partners. R&D plan for the novel technologies, in particular for the crab cavities required to realize the full potential of the LHC upgrade foreseen by 2021.

Speaker: Prof. Lucio Rossi (CERN)

Slides Rossi_HL-LHC_and_CRAB_15Dec2010.pdf Rossi_HL-LHC_and_CRAB_15Dec2010.pptx

10:00 Discussion

10:10 → 10:30 Coffee break

10:30 → 12:10 Optics & Beam Physics Aspects

10:30 Upgrade optics with crab cavities

Review of the main LHC optics constraints. New flexible upgrade optics and its beta* reach. Possible LHC baseline layout wtih crab cavities. Choice of beta*'s and crossing angle with local crab cavities. Optics consistency check and chromatic correction scheme. Potential crab cavity locations and the crab voltage required. Longitudinal space constraints. Transverse mechanical aperture requirements together with expected closed orbit excursion. Possible effects on dynamic aperture, synchro-betatron resonances and long-range beam beam, with associated nonlinear field tolerances.

Speaker: Riccardo De Maria (CERN)

Slides workoutline.pdf

10:50 Effect of non-zero dispersion

Effect of non-zero dispersion for a local crab crossing scheme for the LHC is considered and its impact on stable working point in the presence of crab cavities is analysed. The maximum allowed dispersion (and slope of dispersion?) at the crab-cavity is estimated. Effects of higher order optical aberrations and RF curvature, and their impact on the IR region optics and working point are also considered.

Speaker: Prof. Georg Hoffstaetter (Cornell University, LEPP)

11:10 Impedance effects during injection, energ ramp & store

Review of longitudinal and transverse impedance budgets for the LHC energy cycle. Assessment of crab-cavity impedance spectrum for LHC compatibility.

Speaker: Elena Chapochnikova (CERN)

Slides Crab2011_ES.pdf Crab2011_ES.pptx

11:30 Luminosity leveling with crabs

Concept of lumonisity leveling and the effect of luminosity leveling with crab cavities at ultimate bunch intensities. The use of crab cavities for smaller than nominal emittances for operation with total beam-beam tune shifts of 0.02 to 0.03.

Speaker: Guido Sterbini (CERN BE-ABP)

Slides CC.pdf

11:50 Very large crossing angle & magnet technology

Assuming a successful implementation of the crab scheme with the current IR focusing layout, a future outlook with concepts and associated challenges for the magnet technology to devise independent focusing channels at the IRs for the two beams with larger-angle crab crossing. This could alleviate long range beam-beam problems and enable easier optics solutions for reducing beta*.

Speaker: Dr Ezio Todesco (CERN)

Slides et_crab_1210.pdf et_crab_1210.pptx

12:10 → 14:05 Lunch

14:05 → 15:45 Cavity Technology

14:05 ICFA deflecting cavity workshop summary

A summary of the workshop held on Sept 1-3, 2010 to review the current state of the art deflecting cavity technologies and their application in high energy collider (LHC, KEK-B, ILC, CLIC, LHeC), generation of short x-ray pulses in synchrotron light sources (APS, Spring-8), beam manipulations, emittance exchange and diagnostics. Strategies on cavity design optimization and challenges confronting novel concepts.

Speaker: Dr Alireza Nassiri (Argonne National Laboratory - DOE)

Slides McIntosh_-_Crab_Workshop_Summary.pdf McIntosh_-_Crab_Workshop_Summary.ppt

14:25 EuCARD cavity developments

The development of the 4-rod cavity at 400 MHz toward a crab cavity for the LHC. Detailed cavity-coupler design including deflecting mode characteristics, HOM spectra and achievable damping, coupler configurations, mechanical tolerances, tuning concepts, multipacting and non-linearity of deflecting voltage with transverse offset. Additionally cavity fabrication, treatment, assembly of coupler, Helium vessel and ancillary equipment should be foreseen within the design concept.

Speaker: Graeme Burt (Cockcroft Institute)

Slides LHC10_GB_v1.2.pdf LHC10_GB_v1.2.pptx

14:40 LARP cavity developments

The development of the single rod half-wave cavity at 400 MHz toward a crab cavity for the LHC. Detailed cavity-coupler design including deflecting mode characteristics, HOM spectra and achievable damping, coupler configurations, mechanical tolerances, tuning concepts, multipacting and non-linearity of deflecting voltage with transverse offset. Additionally cavity fabrication, treatment, assembly of coupler, Helium vessel and ancillary equipment should be foreseen within the design concept.

Speaker: Zenghai Li (SLAC)

Slides zli-lhc-cc10-dec-2010.pdf

14:55 KEK cavity developments

Detailed cavity-coupler design including deflecting mode characteristics, HOM spectra and achievable damping, coupler configurations, mechanical tolerances, tuning concepts, multipacting and non-linearity of deflecting voltage with transverse offset. Additionally cavity fabrication, treatment, assembly of coupler, Helium vessel and ancillary equipment should be foreseen within the design concept.

Speaker: kenji hosoyama (KEK, High Energy Accelerator Research Organization)

Slides KEKB_Crab_Cavity_Development.pdf KEKB_Crab_Cavity_Development.ppt

15:10 ODU/JLab cavity development

The development of the parallel bar cavity at 400 MHz toward a crab cavity for the LHC. Detailed cavity-coupler design including deflecting mode characteristics, HOM spectra and achievable damping, coupler configurations, mechanical tolerances, tuning concepts, multipacting and non-linearity of deflecting voltage with transverse offset. Additionally cavity fabrication, treatment, assembly of coupler, Helium vessel and ancillary equipment should be foreseen within the design concept.

Speaker: Jean Delayen (Thomas Jefferson National Accelerator Facility)

Slides ODU-JLab_Parallel_Bar_-_LHC-CC10.pdf

15:25 The Quarter Wave Resonator as a Crabbing Cavity

Speaker: Ilan Ben-Zvi (Brookhaven National Laboratory)

Slides QWR_crab.pdf QWR_crab.ppt

15:35 Discussion, Cavity Technology

15:45 → 16:00 Coffee break

16:00 → 18:00 Cryomodule & Instrumentation

16:00 Slim elliptical cavity at 800 MHz for local crab crossing

A slim highly eccentric elliptical cavity with vertical deflection at 800 MHz, compatible to beam line distances everywhere in the LHC ring, was designed; it is a good fall-back solution in case of problems with new compact 400 MHz designs. RF characteristics of the deflecting mode, HOM spectra and damping, tuning and multipacting are presented.

Speaker: Luca Ficcadenti (INFN)

Slides draft.pdf draft.pptx

16:20 Coupler (FPC & HOM) concepts for compact cavities

Review the current design aspects of the fundamental power coupler and HOM couplers for the compact cavity designs. Feasibility and robustness of such couplers for the LHC crab cavity from the perspective of HOM damping, fabrication, assembly and operation is considered. These concepts are compared to the conventional coupling and damping systems for cavity-coupler concepts.

Speaker: Wolfgang Weingarten (CERN)

Slides Weingarten_crab_cavity_couplers.rev.pdf Weingarten_crab_cavity_couplers.rev.pptx

16:40 Thermal & mechnical analysis for compact cavities

Thermal and mechanical consideration for the compact cavities under considered for the LHC as compared to the conventional cavities in accelerators. General mechanical and thermal considerations for cryomodule hosting the compact cavities, including modelling tools, stress analysis, tuning, alignment, impact of the accelerator environment, issues and input for LHC cavity designs

Speaker: Vittorio Parma (CERN)

Slides crab_cavities_talk_December_2010.pdf crab_cavities_talk_December_2010.pptx

17:00 Tuner concepts for compact cavities

Review of the state of the art tuning systems for SRF cavities in accelerators and potential robust concepts for compact cavity designs to achieve both slow and fast tuning range and tolerances. Design aspects, cryomodule integration and operational considerations including potential issues for the tuning concepts considered for the compact cavities.

Speaker: Dr Alireza Nassiri (Argonne National Laboratory - DOE)

Slides LHC-CC10_TunerConcepts_Nassiri_Final.pdf

Thursday, 16 December

08:30 → 10:10 Crab Cavity Beam Studies

08:30 KEK-B noise experiments

Dedicated beam experiments in KEKB with crab cavities with induced noise to study the impact on beam quality, lifetime and luminosity. The observations of beam-beam instability between the sigma and pi modes and simlations to explain this phenomena is presented. Tolerances based on KEKB measurements for the LHC is derived. The first measurement of crab dispersion using orbit differences with and without crabs is compared to the model.

Speaker: Rogelio Tomas (CERN)

Slides SLIDES.pdf

08:50 SPS beam tests with crab cavities

Feasibility study of KEK-B crab cavities for beam tests in the LHC, infrastructure, cryogenics, collimator configuration and physics objectives for crab cavity tests in the SPS. First results from SPS beam experiments as preparatory steps for a future crab tests in the SPS.

Speaker: Dr Elias METRAL (CERN)

Slides SPSBeamTestsWithCrabCavities_EM.pdf

09:10 Beam simulations for SPS tests

Crab cavities are foreseen to be tested in the SPS as a proof of principle before a full implementation in the LHC. Simulated effects of a single crab cavity on the SPS hadron beam, including ideal energy, stable working points, effect of non-zero dispersion, emittance growth and lifetime for crab tests in the SPS. Comparisons to the recent experiments in the SPS for emittance lifetime during a coast at 55 GeV/c without crab cavities.

Speaker: Hyung Jin Kim (FNAL)

Slides lhc-cc10-sps-crab.pdf

09:30 SPS (and LHC) instrumention for crabbed beams

Available instrumentation in the SPS and LHC to measure signature of crabbed beams, crossing angles in LHC, crab dispersion and head-tail closed orbits. Beam measurements of crab cavity amplitude and phase control using closed orbit distortion, orbit offsets at IP and luminosity measurements, orbit control and feedback near crab cavities and other instrumentation used for crab tests and operation.

Speaker: Marek Gasior (CERN)

Slides 2010-12-15_CrabCavity_Instrumentation.pdf

09:50 Discussion, Beam tests & Technology choice for SPS

10:10 → 10:30 Coffee break

10:30 → 12:30 Machine Protection

10:40 Machine Protection Specifications

Speaker: Dr Jorg Wenninger (CERN)

Slides MPS-Crabs10.pdf MPS-Crabs10.ppt

10:50 How to make crabs LHC safe & collimation compatible

Review of LHC machine protection and LHC collimation system. Constraints and requirements that crab cavities must comply with. Possible approaches for ensuring their compatibility.

Speaker: Daniel Wollmann

Slides 2010-12-16-cc-assmann-vdw.pdf 2010-12-16-cc-assmann-vdw.pptx

11:00 Failure scenarios and mitigation

Crab cavity failures such as abrupt amplitude and phase changes, RF trips, cavity quench are characterized with appropriate time scales. Their potential impact on the LHC beams and mitigation of such failure scenarios within the LHC machine protection constraints is discussed.

Speaker: Joachim Tuckmantel (CERN)

Slides

• FailureScenFormula.pdf
• FailureScenTalk.pdf
• FailureScenTalk.pptx

11:20 KEK-B crab trips & RF signals

Cavity trips and associated RF & beam observations at KEKB. Types of trips, their signature and the (presumed) root causes. Possible mitigation schemes for LHC.

Speaker: Kota Nakanishi (Japan/KEK)

Slides nakanishi_trips.pdf nakanishi_trips.pptx

11:40 LHC studies for RF trips

Results from particle tracking using the LHC collimation system in Sixtrack and MADX to determine local signatures of the particle losses due to abrupt crab cavity failures. Detailed scans to determine specifications on fast cavity failures is derived to ensure machine preotection during the LHC cycle at ultimate intensities. Some aspects of upgrade optics is also studied.

Speakers: Rama Calaga (BNL), Tobias Baer (Universitaet Hamburg)

Slides

• 2010.12.16_-_Fast_Failure_of_LHC_Crab_Cavities.pdf
• 2010.12.16_-_Fast_Failure_of_LHC_Crab_Cavities.pptx
• MP1.pdf

12:00 Interplay of transverse damper and crab cavities

Transverse damper settings in the presence of crabbed beams and beam-beam. The interplay between the damper and the crab cavity for single bunch and bunch trains. Suppression of the effect of phase noise on the beam and of potential instabilities from crab cavities to relax tolerances on crab-cavity RF controls.

Speaker: Wolfgang Hofle (CERN)

Slides CCWS_15DEC_2010.pdf CCWS_15DEC_2010.pptx

12:20 Discussion, Machine Protection

12:30 → 14:00 Lunch

14:00 → 15:40 RF Controls & Testing

14:00 KEKB crab RF architecture & controls

RF system architecture of the KEKB crab cavities including high power RF system and LLRF controls. Amplitude and phase tolerances and stability, compensation of beam loading, closed orbit and beam instabilities. Possible improvements for achieving fewer "RF trips" including operating temperature, design aspects etc..

Speaker: Kota Nakanishi (Japan/KEK)

Slides

• KEKBCrabTripRateFunakoshi.pdf
• KEKBCrabTripRateFunakoshi.pptx
• nakanishi_controls.pdf
• nakanishi_controls.pptx
• nakanishi_controls.pptx

14:20 SM18 test stand for crabs

Cryomodule assembly options at CERN, test stand for low power and high power testing, high power RF availability, availability of cryogenics, gradient performance, cavity-coupler conditioning, instrumentation, mechanical, transport issues and quality control.

Speaker: Olivier Brunner (CERN)

Slides Crab_Cav_Workshop_dec'10.pdf

14:40 Cryogenics for SPS, LHC & SM18

Operating temperature options, crab specific cryogenics at IR1, IR5, IR4, SPS & SM18, Helium pressure and availability, cryo circuits and controls, safety valves and protection, overall installation effort,cost and time line, heat loads, impact on the overall LHC during regular operation

Speaker: Bruno Vullierme (CERN)

Slides CC_cryo_inst_2010_REV.pdf CC_cryo_inst_2010_REV.pptx

15:00 LLRF considerations for Crab Cavities

I will first briefly present the LHC reference RF generation (one per ring) and the LLRF field control (one system per cavity). I will then concentrate on the issue of RF phase noise: The performance achieved with the LHC cavities will be presented in details and we will try to extrapolate these results to the Crab Cavities. A possible interfacing of the Crab Cavities with the 400 MHz reference RF and with the Control System (Functions) will be described. The operational scenario will then be outlined: RF controls to make a detuned crab cavity at "zero" voltage invisible to the beam over the LHC injection and ramp while retuning and gradually ramping the cavity voltage over the course of a physics store to perform luminosity leveling. Finally a candidate prototype LLRF system will be presented.

Speaker: Philippe Baudrenghien (CERN)

Slides CC2010LLRF_v2.pdf CC2010LLRF_v2.pptx

15:40 → 16:00 Coffee Break

16:00 → 18:00 Schedule & Future Outlook

16:00 Field quality and non-linearity of deflecting mode 20'

Due to the high beta functions at the location of the local crab cavities, there is a stringent limit on the maximum allowable non-linearities of the deflecting field. Field quality and higher-order harmonics for a conventional ellitpical crab cavity and for LHC compact crab cavities are analysed, and their impact on the cavity design is considered. Aspects related to beam loading due to transverse offset and phase jitter are also addressed.

Speakers: Dr Erk Jensen (CERN), Rama Calaga (BNL)

Slides RFNONLIN.pdf talk.pdf

16:20 Overall planning of RF infrastructure

Outline of the crab cavity work package within the HL-LHC upgrade including the potential collaborators, distribution of R&D tasks, time line for R&D and construction, cost estimate over the duration of the project, and man power estimates.

Speaker: Dr Erk Jensen (CERN)

Slides

• CC10_EJ.pdf
• CC10_EJ.pptx
• SummaryCavtechCryostat.pdf
• SummaryCavtechCryostat.pptx

16:40 LHeC, HE-LHC other crab cavity applications

Possible future crab-cavity applications, including their merits and rough parameters, for HL-LHC, LHeC, HE-LHC, ILC, CLIC, and other projects.

Speaker: Dr Frank Zimmermann (AB/ABP)

Slides Future_Applications_of_Crab_Cavities.pdf Future_Applications_of_Crab_Cavities.pptx

17:00 Place Holder

17:20 Discussion, Schedule, Planning & Future

Friday, 17 December

14:00 → 15:40 Summary Sessions I

14:00 LHC-CC Status & Review

Speaker: Jean-Pierre Koutchouk (CERN)

Slides LHC-CC10_Session_1_jpk.pdf LHC-CC10_Session_1_jpk.pptx

14:20 Optics & Beam Physics Aspects

Speaker: Dr Massimo Giovannozzi (CERN)

Slides giovannozzi_Summary_Session_II.pdf giovannozzi_Summary_Session_II.ppt

14:40 Cavity Technology

Speaker: Edmond Ciapala (CERN)

Slides SummaryCavtechCryostat.pdf SummaryCavtechCryostat.pptx

15:00 Cryomodule & Instrumentaion

15:40 → 16:00 Coffee Break

16:00 → 17:40 Summary Sessions II

16:00 Crab Cavity Beam Studies

Speaker: Paul Collier (CERN)

Slides CC-Worshop_Summary.pdf CC-Worshop_Summary.pptx

16:20 Machine Protection

Speaker: Dr Jorg Wenninger (CERN)

Slides MPS-Crabs10.Summ.pdf MPS-Crabs10.Summ.ppt

16:40 RF Controls & Testing

Speaker: Jean Delayen (Thomas Jefferson National Accelerator Facility)

Slides RF_CONTROL_AND_TESTING_SUMMARY.pdf RF_CONTROL_AND_TESTING_SUMMARY.pptx

17:00 Schedule & Future Outlook

Speaker: Roland Garoby (CERN)

Slides Summary_Schedule_and_Outlook.pdf Summary_Schedule_and_Outlook.ppt

17:40 → 18:30 Advisory board discussion