TATIONpRÆSEN

ESS TAC, 5-6 Nov, 2014

AARHUSUNIVERSITET

High Energy Collimator Recommendation

H.D. Thomsen, S.P. Møller (ISA, Aarhus University)

M. Eshraqi, R. Miyamoto, E. Laface, T. Shea, E. Pitcher, A. Nordt,L. Lari, L. Tchelidze, H. Danared, P. Ladd (ESS)

S. Wronka, K. Szymczyk, P. Warzybok (NCBJ, Swierk)

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HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

HEBT Layout + Collimator Baseline

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μx,y = 60°

≠Neutron Shield Wall!Single-stage

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

Beam Expander System

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Focusing = (Lin. – non-lin)

PBW

Dogleg

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITETCollimator Workshop, 13-14 May, ESS:

“Beam Losses and Collimators in Transfer Lines”

› 11 external experts at hand: CERN (6), SNS (1), KEK (1), PSI (2), GSI (1)

› Uncontrolled losses? Focus on ~2 GeV› If possible, beam should be stopped at lower energies.

› Solution & experience sharing! Collimation strategies?

› Visiting labs: collimators are being used to (HDT’s impression):› Reduce operational beam losses: Prepare the beam for a next-stage accelerator (typically

ring-based)› Protect sensitive accelerator hardware (e.g. SC magnets)› Clean beam downstream of parasitic secondary beam production targets (PSI)

› Workshop recommendations:› Experience from similar operating facilities should be studied with the SNS being the lead

candidate.

› Beam physics studies should be performed to fully determine the need for collimation. Be very specific in purpose! Every-day operation & infrequent catastrophic events.

› If possible, consider a more global collimation strategy, i.e. MEBT + HEBT collimator performance?

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R. Bruce, 2014.04.15

General design considerations

When designing an accelerator facility:

• Do we need collimators?

• Where should collimators be installed?

– Global/local protection?

– Betatron / momentum collimation?

• Multi-stage system?

• Movable devices or fixed masks?

• What material?

• What simulation tools do we have?

• Design choices depend on losses we want to protect against

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

Inter-Diciplinary Ad-Hoc Working GroupKick-off meeting late August.› ISA, Denmark: H.D. Thomsen, S.P. Møller

› ESS: M. Eshraqi, R. Miyamoto, E. Laface, T. Shea, E. Pitcher, A. Nordt, L. Lari, L. Tchelidze, H. Danared, P. Ladd, S. Molloy

› NCBJ, Poland: S. Wronka, K. Szymczyk, P. Warzybok

› Linac + HEBT beam physics, beam instrumentation, target, machine protection, beam loss simulations & shielding, vacuum, mechanical design, …

Conclusive proposal:› No clear justification for the existing HEBT collimator systems. Remove

them from the ESS baseline design.

› Reducing the overall project contingency a tiny degree.

› Continue collimator design, but not construction, to be prepared for surprises?› (Another discussion: how far?)

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HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

A SIMILAR FACILITYThe Oak Ridge Spallation Neutron Source

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M. Plum – ESS Beam Losses and Collimation wkshp May 2014

8 Managed by UT-Battellefor the U.S. Department of Energy

SNS Scrapers and collimator locations

RTBT

HEBT

Injection

Extraction

RF

Collimators

In MEBT:Left-right, top-bottom scrapers

In HEBT:Two pairs of left-right scrapersTwo pairs of top-bottom scrapersTwo collimators

In HEBT:Left-right (high and low momentum) scrapersFollowed by beam dump

In Ring:Four scrapers (0, 45, 90, 135 deg.)Three collimators

Most effective

Occasionally used

Scrapers almost never used

Rarely used

In RTBT:Two collimators Target protection

ESS – no ring:

• Small emittance

• Strictly single-pass

• Beam quality?

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

ESS (5 MW, p) vs. SNS (1.4 MW, H-)?

Shishlo et al., IPAC'12, TUOBA03 (2012), Intra-Beam Stripping (IBST):

The reduced beam loss for protons implies that a proton SCL should be able to provide several times higher power with the same low activation and ``hands on'' maintainability as the existing SNS linac.

SNS HEBT? Beam debunches -> IBST not a concern.

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H-

p

H-, Ip2

p, Ip

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

BEAM STUDIESOperational Beam Losses: activation, material deterioration, etc.

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HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

Simulating the HEBT Halo?

Injection @ HEBT s = 0› Two-component beam, (core + halo)› Typically 2 x Gaussians› εh / εc = 5› Nh / (Nh+Nc) = 1%› 6D: transverse +

longitudinal

End-to-End, ESS Acc. Phys.› 4D Gaussian is fed into the RFQ

› MEBT->DTL->SCL->HEBT

› Time-consuming but can be rewarding (long. effects)

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Errors (stat + dyn) can be applied to both approaches

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

Injection: HEBT Error Studies

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IPAC’14, WEPRO074:• 1000 HEBTs x 106 particles: STAT (+ corr) + DYN Errors• No losses until target monolith (<100 W)

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

End-to-End (ESS Beam Physics Group)

HEBT:›Low-energy protons (300-600 MeV)

›E < 800 MeV are lost inside the first dipole

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RFQ output

R. Miyamoto, HB2014, MOPAB18

+Errors

103x105

-Errors

1x107

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

Also seen @ SNS Achromat to Ring?

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mrem / hr

10 mSv/h

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

“Alternative”: Normalized HEBT Aperture

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SNS HEBT: 15 – 24 @ 1.4 MW

APT HEBT: 80 @ 100 MW

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

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HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

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AARHUSUNIVERSITET

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HEB

T A

pert

ure

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

BEAM STUDIESAccidental Beam Losses: accelerator component damage

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HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

Timescales of Component FailureInitiating event: The failure of an accelerator component leads to dramatic beam parameter changes.

Result: Beam losses are increased dramatically at downstream (key) locations. Collimators can buy time before beam-induced accelerator component damage.

Timescale τf of the initiating event is important in order to determine response time of mitigating system.

› FAST: τf < 2.86 ms, beam parameters can change considerable during a pulse› RF (arcing)› Low-inductance magnets (raster system?)

› MODERATE: τf > 2.86 ms, impact can build up over a number of pulses› High-inductance magnets (conventional magnets) 19

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

Case 1: RF Failure, ∆E = 0 MeV

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∆y < 0.33 mm/MeV

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

Case 1: RF Failure, ∆E = -100 MeV

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∆y < 0.33 mm/MeV

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

Case 1: ∆E, Impact @ BEW

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HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

“Alternative”: Machine Protection

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Beam can be inhibited within ~20 µs(133 µs of beam corresponds to 1 SNS pulse)

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

Summary› No universal collimator design available: focus on actual problem(s) in

our unique machine!› SNS:

› H- problem: irrelevant to collimation questions› HEBT collimators only applied to make small improvements to the beam losses.› MEBT scraper system has been upgraded.

ESS status & actual problems?› Transverse halo: does not seem to be a problem. Ample apertures are

used.›BES suppresses beam distribution (quality) + no second-stage accelerator› Upstream dogleg dipole will filter out low-energy tail. May be

“considerable” (~10 W/m)? › Accidental beam failures: passive machine protection

› HEBT collimators cannot provide global protection

Proposal:› Remove HEBT collimators from the ESS baseline› Design. Build if found necessary (latency!)› Pursue the issue with the upstream dipole

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HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

EXTRA SLIDES

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HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

E2E Error Magnitudes

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HB2014, MOPAB18

RFQ beam errors

Element errors

HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

BEAM STUDIESMEBT Scraper System?

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HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

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AARHUSUNIVERSITET

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HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

71 ms failure in QP6

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HEINE DØLRATH THOMSENESS TAC, 5-6 Nov,

2014

AARHUSUNIVERSITET

71 ms failure in QP6

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33 Managed by UT-Battellefor the U.S. Department of Energy

M. Plum – ESS Beam Losses and Collimation wkshp May 2014

Some sample H+ beam profiles in the SNS HEBT

Horizontal Vertical

Profiles measured Dec. 22, 2013

Non-Gaussian tails / halo appear beginning at ~1/10 of peak

Solid lines show Gaussian fits to the data

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34 Managed by UT-Battellefor the U.S. Department of Energy

M. Plum – ESS Beam Losses and Collimation wkshp May 2014

More H+ beam profiles in the SNS HEBT

Horizontal Vertical

Profiles measured April 6, 2014

Non-Gaussian tails / halo appear beginning at ~1/10 of peak

Solid lines show Gaussian fits to the data

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