Beam losses in the CLIC drive beam: specification of acceptable level and how to handle them

Beam losses in the CLIC drive beam: specification of acceptable level and how

to handle them

ACE 2010 02 04Michael Jonker

Beam loss detection and Radiation issues. (in the main tunnel)

BLM system primary purpose: detection of onset of slow losses.

Operational beam loss background levels:• Tails on the beam entering the main linac and decelerators• Interaction with residual beam gaz.Loss levels limits• From Beam Physics: 0.1 % main beam, 0.1% each drive train• From Radiation damage over the lifetime of CLIC (1MGy/year see following slides)Hence, these limits will define the required vacuum performance• Resolution at operational background levels 20 % ?

Dangerous level of beam loss when 10-2 of DB or 10-4 of MB is lost on an single aperture restriction. (Rough estimate needs further detailed simulations)

Extended range for catastrophic (fast) losses: diagnostics only. (i.e. to better understand what happened, if ever something should happen)

Effect of beam in matterNote: in energy density in cupper for Melting : 400 J g-1, Structural yield 62 J g-1

Material C Al Cu W

LEP Beam (100GeV, 445 nC)Energy Density @ shower core [J g-1] 0.64 1.68 22 112Energy Density @ IB 0.1 mm2 [J g-1] 778 719 624 510

CLIC Main Pulse (1.5 TeV, 186 nC, @ collimators)Energy Density @ shower core [J g-1] 3 9 122 614

Energy Density @ IB 40 mm2[J g-1] 8.3 105 7.7 105 6.7 105 5.4 105 2.2 103 /bunch

CLIC Main Pulse (2.8 GeV, 204 nC @ DR septum) Energy Density @ shower core [J g-1] 0.01 0.03 0.34 1.6

Energy Density @ IB 125 mm2 [J g-1] 2.3 105 2.2 105 1.8 105 1.5 105 600 /bunch

CLIC Drive Train (2.4 GeV, 24545 nC)Energy Density @ shower core [J g-1] 1.34 3.08 40 187

Energy Density @ IB 1 mm2 [J g-1] 4293 3964 3444 2810

03.12.2009 CLIC OMPWG

Beam losses (DB 2.4 GeV)

2.4 GeV Lost before QP

1.5 TeV Lost in QP

S. Mallows, T. Otto, CLIC Two-Beam Module Review, September 2009

03.12.2009 CLIC OMPWG

Permitted fractional loss model (New model, Drive beam)

Loss point Beam dynamics

Old estimate

New Estimate

in QP 1.25 E-6 1.0 E-7 1.6 E-6before QP 1.25 E-6 -- 2.1 E-6in PET 1.25 E-6

Loss point Beam dynamics

Old estimate

New Estimate

in QP 1.25 E-6 4.7 E-7 1.9 E-5before QP 1.25 E-6 -- 2.0 E-5in PET 1.25 E-6 4.8 E-5

2.4 GeV

0.24 GeV

Based on radiation limits of magnets during 10 years x 6 month operation.Regular magnet design (no rad hard)

Type of failures• Failures causing slow onset of losses

– Magnet system– Vacuum system (performance defined by tolerable operational losses)

– Slow drifts (alignment, temperature, …)Next pulse permit and safe by design(2 ms)

• Failures causing fast losses (“in-flight” failures)

– RF breakdown (effects on the beam under study)– Kicker misfiring (turn around kickers !)– Klystron trips (not applicable for DB)

Protection by fixed masks (Impedance?)