KEK j-PARC ! LINAC Collaboration: Initiating Yong Liu 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 Materials and Life Science Hadron Experimental Experimental Facility (MLF) Facility 3-GeV Rapid-Cycling Synchrotron, RCS (Circumference 350m � ADS: Accelerator Driven Nuclear Waste Transmutation System (in the 2 nd phase) Linac (400MeV) Main Ring Synchrotron, MR (330m) Neutrino Experimental (30-50 GeV) Facility � Circumference 1600m) �-�����-������ �������� Joint Project between KEK and JAEA
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 90-deg dump J-PARC linac consists of 100-deg dump • 50-keV negative hydrogen ion source à RF ion source • 3-MeV RFQ à RFQ3 RCS injection • 50-MeV DTL (Drift Tube Linac) • SDTL (Separate-type DTL) 181-MeV à 190MeV Injection section • 400 MeV ACS (Annular Coupled Structure Linac) 2 nd Arc Collimator section MEBT2 Front-end 1 st Arc 30-deg dump (7 m) SDTL(+SDTL16) ACS section DTL (27 m) (84 m) (109 m) 0-deg dump 181 MeV 400MeV 3 MeV 50 MeV 50m à 190MeV à 50mA Front-end = IS + LEBT+ RFQ + MEBT
Roadmap of J-PARC LINAC Intensity Upgrade 5 181/190MeV 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: 50 à 60mA or/and 500 à 600us: aim at 1.2/1.5MW@MLF 1 st Trial of 60mA: Jul.5 2017: 68mA(IS) 62mA(MEBT1) • 2 nd Trial of 60mA: Dec.25,26 2017 60mA(DTL no accel. ), 57mA(Li) • 3 rd 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 (4 th Trial ), 500us injection to RCS : Dec. 26, 2018 (~1.2MW@RCS) •
Initiating LINAC collaboration: possible projects
J-PARC LINAC Layout and Matching Scheme 90-deg 7 sections with transverse measurement in J-PARC linac 100-deg dump -- 6 with transverse matching To RCS dump --5 � 2D + 1 � 3D matching (now 2D) INJ WSM+ MEBT2-ACS matching section Match with Matching MEBT2-B1, B2 + L3BT-SCR Q07~10 (or Q09~12) WSM+ DB2 BSM#1 WSM#1 BSM#2 WSM#2 BSM#3 WSM#3 WSM#4 Matching+ Collimation ACS01 ACS02 ACS03 ACS04 MEBT2 ACS L3BT-ARC WSM+ Matching WSM+ L3BD0 WSM WSM+ BSM+ WSM+ Matching Matching 30-deg 3D Matching Matching Not available IS dump RFQ DTL SDTL ACS DB1 0-deg LEBT MEBT1 MEBT2 dump 324MHz à 972MHz
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 Planned MEBT2-ACS 3D matching scheme BSM#1 WSM#1 BSM#2 WSM#2 BSM#3 WSM#3 WSM#4 ACS01 ACS02 ACS03 ACS04 MEBT2 ACS • 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 à Possible help on electronics etc. from Fermilab
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)
Observed Typical Halo in J-PARC LINAC in Early Time r rms ≤ r sig. ACS;191MeV 25mA SDTL,50MeV,25mA 2014.1.23 2014.1.23 r rms > r sig. Comparison 400MeV,25mA 181MeV,25mA 2014.1.23 2013.4.14
Observed Halo Evolution in J-PARC LINAC Early Time Increase from design Halo collimation 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
Countermeasures against Halo • Improve matching accuracy • Avoid resonances • Halo collimation system is installed in L3BT downstream (for <0.5% of 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 19 Simulated envelope T=1.0, E 0 100% T=0.3, E 0 100% Accumulated loss rate T=1.0, E 0 96% T=0.3, E 0 96% For 50mA operation with optimized emittance 0.1W/m Accumulated loss power IBSt loss power is close to 0.1W/m at ACS 0.675% duty T=0.3 helps to reduced more than 50% Stability?
Tune Diagram for J-PARC LINAC ACS (191~400MeV) 20 Transverse redesign T=1 Baseline design Longitudinal redesign “Temperature ratio” ! ! ! ! ! ≡ ! ! = ! ! ! ! ! ! Stronger quad setting or weaker longitudinal focusing ! ! ! ! ! ! ! ! ! ! !
21 Experiment Results for Resonance � IBSt Mitigation at ACS Beam Study on Oct.10, 2016. 40mA, ε x,y|nrms =0.3mm*mrad, ε z|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 Unstable Previous best Comparison Stabilized Stabilized Near z-accept. ACS01 ACS21
Status of Main Residue Radiation & 22 Aperture Rearrangement at ACS The way toward mitigation of residue radiation • Status of main residue radiation Hottest region � 200MeV~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)
Abnormal Residue Radiation and Aperture Re-arrangement 23 Shown in ATAC2016 Abnormal regularity of residue radiation at ACS S/F � φ37 � -> S/F � φ40 � since very beginning at � & � F � φ37 � -> Ti-duct � φ37 � �� Reason 1: CT aperture is 3mm less than else ACS11 S/F � φ37 � unchanged �� F � φ37 � unchanged Reason 2: CT materials is vulnerable to radioactivation �� S/F � φ37 � -> S/F � φ40 � ��� F � φ37 � -> Ti-duct � φ40 � �� �� � � �� 4 1 0 � � 2 C ACS# A T A ACS05 ACS12~21: zigzag flattened, � ~ � and mitigated n S/F � φ37 � unchanged i ACS11: good comparison � < � and increased n F � φ37 � -> Ti-duct � φ37 � w ACS05: � > � (relation changed) o h Compared with data May. 20 and Nov. 12 ACS01~04, 06~10: � > � (relation changed) S Empty duct FCT+SCT, FCT May. 20 � < � Abnormal large � : ACS04,07, 08 Aperture re-arrangement 2015 : Latter half: aperture increase, FCT � removed aperture increase in #4,7,8, etc. A B � � � � Aperture re-arrangement 2018 : All the rest: aperture increase, FCT � removed All aperture à Φ 40
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