LINAC Collaboration: Initiating Yong Liu KEK/J-PARC Mar. 19, 2019 - - PowerPoint PPT Presentation

LINAC Collaboration: Initiating

Yong Liu KEK/J-PARC

KEK j-PARC!

• Mar. 19, 2019 Fermilab

Outlines

• J-PARC & Roadmap of LINAC Intensity Upgrade
• Initiating LINAC collaboration: possible projects

Important monitors to be improved, eg. bunch shape monitor (BSM) Drift tube renewal Low-energy beam loss detection for commissioning, neutron detector/scintillation Beam physics Beam experiment (online and in J-PARC RFQ test stand) Beam 2D/3D measurement, collimation, beam notch/chop, etc.

• Conclusion and outlook

J-PARC Facility Layout at Tokai

Main Ring Synchrotron, MR (30-50 GeV) Circumference 1600m) Linac (400MeV) (330m) 3-GeV Rapid-Cycling Synchrotron, RCS (Circumference 350m Hadron Experimental Facility Materials and Life Science Experimental Facility (MLF) Neutrino Experimental Facility Joint Project between KEK and JAEA

• -

ADS: Accelerator Driven Nuclear Waste Transmutation System (in the 2nd phase)

J-PARC linac consists of

• 50-keV negative hydrogen ion source àRF ion source
• 3-MeV RFQ àRFQ3
• 50-MeV DTL (Drift Tube Linac)
• SDTL (Separate-type DTL) 181-MeV à190MeV
• 400 MeV ACS (Annular Coupled Structure Linac)

Front-end (7 m)

J-PARC Linac Layout and Upgrade Scheme

181/190MeV à 400MeV: installation in 2013 Summer, accomplished in Jan., 2014 15/30mA à 30/50mA: on-line in 2014 Summer, accomplished in Oct. 2014

SDTL(+SDTL16) DTL 0-deg dump 30-deg dump Front-end = IS + LEBT+ RFQ + MEBT (84 m) (27 m) 50 MeV 181 MeV à190MeV 3 MeV 100-deg dump 90-deg dump RCS injection

1st Arc 50m Collimator section 2nd Arc Injection section

MEBT2

ACS section

400MeV à50mA (109 m)

Roadmap of J-PARC LINAC Intensity Upgrade

• 181/190MeV à 400MeV: Jan., 2014

Operation/Study 15/30mA à 30/50mA: Oct. 2014 è 400MeV, 50mA: ready for 1MW from RCS (Demo:Dec.2014)

• -------------------- Design accomplished ---------------------
• 40mA in Operation: Jan. 2016

Next step: 50à60mA or/and 500à600us: aim at 1.2/1.5MW@MLF

• 1st Trial of 60mA: Jul.5 2017: 68mA(IS) 62mA(MEBT1)
• 2nd Trial of 60mA: Dec.25,26 2017 60mA(DTL no accel. ), 57mA(Li)
• 3rd Trial of 60mA: Jul.3, 2018 62mA(Li)
• 50mA in Operation: Oct. 2018
• 50mA, 600us injection to RCS : Oct. 19, 2018 (~1.2MW@RCS)
• 60mA (4th Trial ), 500us injection to RCS : Dec. 26, 2018 (~1.2MW@RCS)

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Initiating LINAC collaboration: possible projects

J-PARC LINAC Layout and Matching Scheme

ACS

30-deg dump 0-deg dump 90-deg dump 100-deg dump To RCS

DTL DB1 DB2 RFQ SDTL IS LEBT MEBT1 MEBT2 WSM

Matching Not available

WSM+

Matching

WSM+ BSM+

3D Matching

L3BD0 WSM+

Matching

L3BT-SCR WSM+

Matching+ Collimation

INJ WSM+

Matching

L3BT-ARC WSM+

Matching

WSM#1

ACS01

WSM#2

ACS02

WSM#3

ACS03

WSM#4

ACS04

BSM#2 BSM#1 BSM#3

Match with MEBT2-B1, B2 + Q07~10 (or Q09~12)

MEBT2 ACS

7 sections with transverse measurement in J-PARC linac

• - 6 with transverse matching
• -52D + 1 3D matching (now 2D)

MEBT2-ACS matching section

324MHzà972MHz

List of Possible Collaboration Projects in LINAC

• Bunch Shape Monitor
• Drift Tube
• Beam loss monitor, esp. low-energy beam loss

detection for commissioning, neutron detector/scintillation

• Beam physics
• Beam experiment (online and in J-PARC RFQ test stand)

Beam 2D/3D measurement, collimation, beam notch/chop, etc.

J-PARC BSM Development Status

• Three BSMs from INR, but uninstalled from ACS due to

vacuum problem

• J-PARC made 3 new BSMs for MEBT2-ACS (191MeV),

1 in MEBT1 (3MeV) and 1 in L3BT (400MeV), all in test àPossible help on electronics etc. from Fermilab

WSM#1

ACS01

WSM#2

ACS02

WSM#3

ACS03

WSM#4

ACS04

BSM#2 BSM#1 BSM#3

Planned MEBT2-ACS 3D matching scheme

MEBT2 ACS

J-PARC L3BT BSM (400MeV)

J-PARC L3BT BSM (400MeV)

Brief Introduction of Beam Physics Issues in J-PARC LINAC

• Matching improvements, halo
• Dominant source of beam loss: IBSt
• Aperture problem

Emittance Growth and Halo Studies: Remained Problem

• 7 sections with transverse measurement in J-PARC linac

6 with transverse matching with rms-envelope-based online model Online model, PIC simulation and measurement are consistent (locally) Online model: XAL <=> Trace3d; simulation: IMPACT Online matching of MEBT1 (3MeV) is NOT realized to date Reason: ~20-30% emittance growth ß space charge à Online model does not work well for ~20-30% emittance growth

• MEBT1 matching is achieved by Q-scan + offline procedure

Mismatch is one of main source of emittance growth, halo formation and beam loss

Beam Halo Observed at J-PARC LINAC

Sources of halo in a high intensity hadron LINAC

• Low-energy part from RFQ

à Low-energy loss

• Space charge effect
• Transverse mismatch (esp. MEBT)

à Partly lost at mid-energy, partly survive

• Online longitudinal matching not available (esp.

between freq. jump) à Survive

• Resonances (to avoid if possible)

Comparison 181MeV,25mA 2013.4.14 400MeV,25mA 2014.1.23 SDTL,50MeV,25mA 2014.1.23 ACS;191MeV 25mA 2014.1.23

rrms ≤ rsig. rrms > rsig.

Observed Typical Halo in J-PARC LINAC in Early Time

Almost perfectly matched (according rms emittance) Halo is usually not matched due to space charge From same beam profile one can get rms envelope and envelope by gaussian fit, with above two sets of envelope one can get two emittance Comparison shows halo evolution

Increase from design

Observed Halo Evolution in J-PARC LINAC Early Time

Halo collimation

Countermeasures against Halo

• Improve matching accuracy
• Avoid resonances
• Halo collimation system is installed in L3BT downstream (for <0.5%
• f beam due to beam dump capacity)
• Halo collimation system is also proposed in MEBT1

No significant loss in LINAC due to mismatch and beam halo No observable loss in RCS due to LINAC beam halo

IBSt in J-PARC LINAC

• IBSt@ACS was verified as the dominant source of

beam loss since 2016 by lattice exercises both in simulation and experiment

Comparison of IBSt for ACS Lattices

Accumulated loss power 0.675% duty 0.1W/m

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For 50mA operation with optimized emittance IBSt loss power is close to 0.1W/m at ACS T=0.3 helps to reduced more than 50% Stability?

T=1.0, E0 100% T=1.0, E0 96% T=0.3, E0 100% T=0.3, E0 96% Simulated envelope Accumulated loss rate

T=1 Baseline design Longitudinal redesign Transverse redesign

Tune Diagram for J-PARC LINAC ACS (191~400MeV)

!

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! !!! !

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!!!!

“Temperature ratio”

Stronger quad setting or weaker longitudinal focusing

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Experiment Results for ResonanceIBSt Mitigation at ACS

Beam Study on Oct.10, 2016. 40mA, εx,y|nrms =0.3mm*mrad, εz|nrms ~ 0.38mm*mrad(?) After longitudinal “redesign” Tx/Tz=0.3 was stabilized near Tank level ~95%; Fine tuning is needed For Tank level ~90%, loss happened at later 1/3

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Unstable Previous best Comparison Stabilized Stabilized Near z-accept. ACS01 ACS21

Status of Main Residue Radiation & Aperture Rearrangement at ACS

The way toward mitigation of residue radiation

• Status of main residue radiation

Hottest region200MeV~400MeV, esp. ACS, by IBSt A few hotspots ~3.5mSv/h @surface for MLF@500kW

• Mitigation of beam loss: protection of both person and machine

To improve matching and prevent halo formation Improvement of lattice, e.g., to minimize IBSt

• Localization of beam loss: protection of person, mainly

Remove abnormal hotspots by aperture re-arrangement (geometry and material)

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Abnormal Residue Radiation and Aperture Re-arrangement

Empty duct FCT+SCT, FCT

A B

• Abnormal regularity of residue radiation at ACS

since very beginning

Reason 1: CT aperture is 3mm less than else Reason 2: CT materials is vulnerable to radioactivation

S/Fφ37 -> S/Fφ40 Fφ37 -> Ti-ductφ37 S/Fφ37 -> S/Fφ40 Fφ37 -> Ti-ductφ40 ACS11 S/Fφ37 unchanged Fφ37 unchanged

ACS05 S/Fφ37unchanged Fφ37 -> Ti-ductφ37

ACS12~21: zigzag flattened, ~ and mitigated ACS11: good comparison < and increased ACS05: > (relation changed) ACS01~04, 06~10: >(relation changed) Abnormal large : ACS04,07, 08 ACS# at &

• Compared with data May. 20 and Nov. 12
• May. 20 <

S h

• w

n i n A T A C 2 1 4 Shown in ATAC2016

Aperture re-arrangement 2015: Latter half: aperture increase, FCT removed aperture increase in #4,7,8, etc. Aperture re-arrangement 2018: All the rest: aperture increase, FCT removed All aperture à Φ40

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Residue Radiation at 500kW, Mar.~Jun., 2018

• 500

• 500

• 500

• A

B A B

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500 1000 1500 2000 2500 3000 3500 2018/11/01 2018/11/08 2018/11/15 2018/11/21 2018/12/06

• 500

1000 1500 2000 2500 3000 3500 2018/11/01 2018/11/08 2018/11/15 2018/11/21 2018/12/06

• 500

1000 1500 2000 2500 2018/11/01 2018/11/08 2018/11/15 2018/11/21 2018/12/06

• 500

1000 1500 2000 2500 2018/11/01 2018/11/08 2018/11/15 2018/11/21 2018/12/06

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ACS Residue Radiation at 500kW, Nov.~Dec., 2018 After Aperture Re-arrangement at ACS first Half

H0 Loss-pattern Simulation(1)

Loss-pattern of H0 By IBSt@ACS06 ACS06 W/m

H0 Loss-pattern Simulation(2)

Conclusion and Outlook

• J-PARC LINAC roadmap and activities are reviewed
• Many open questions
• Many possible collaboration projects in LINAC

Let’s start