37th B2GM

Injector linac status and energy margin

Kazuro Furukawa
for Injector Linac Groups<http://www-linac.kek.jp/linac/>< kazuro.furukawa @ kek.jp >Injector linac status and energy

K.Furukawa, Nov.2020

1

24th KEKB accelerator review³Remotely on July 15th and 20thuGeneral recommendations on injector
vPursue aggressive linac/injector improvements …

uInjector recommendations
vImprovements in³Positron capturing section, positron yield³Photocathode for RF gun, electron bunch charge³BT2 for obstacles, beam instrumentations, beam optics

vMostly in line with planned improvements duringsummer
Injector linac status and energy

K.Furukawa, Nov.2020

2MEXT roadmap and injector
uMEXT Roadmap 2020
³HER 2.6 A x LER 3.6 A (original plan before 2020)
w4 nC/bunch, 2 bunch/pulse, 50 Hz, 50% efficiency
could have supported 6 minute lifetime in HER/LERv➡ HER 2.0 A x LER 2.8 A³The same condition supports lifetime down to 240 seconds³ although beam quality has to be maintained

Injector linac status and energy

K.Furukawa, Nov.2020

3Improvements during summer shutdown
u Replacement of thermionic gun cathodeu Replacement of RF gun cathode (Ir7Ce2), removing heating systemu Installation of diffractive optical element (DOE, laser profile shaping), Laser position stabilization
feedbacku Upgrade of event timing controls for continuous laser cleaningu Preparation for secondary RF gun
u Replacement of high power klystron (KL_B4)
u Replacement of klystron solenoid power supply (2)u Replacement of thyratron (KL_A1_B, A2, 15, 16, 17, DS, DN)
u Installation of noise elimination measure (all 60 units)u Replacement of inverter power supply (KL_17, DS)u Improvement to master oscillator with more detectors and phase shifters
u Replacement of driver klystron with solid-state amplifier (SB_B)
u Installation of independent amplifier (KL_C8)
u Pulse-to-pulse amplitude controls at SHB
uu
u
u
u

Replacement of flux-concentrator and nominal operational field (12 kA)
Installation of 4 pulsed steering magnets and 4 bpms inside of positron capturing section
Replacement of charging circuit for all pulsed magnet power supplies
Replacement of old cables for high power magnet power suppliesUpgrade merger beamline after two guns with 2 pulsed bends, 3 quads, 2 bpms and a new chamber

Injector linac status and energy

K.Furukawa, Nov.2020

4Improvements during summer shutdown
u Installation of diffractive optical element (DOE, laser profile shaping), laser position
stabilization feedback, and cathodeu Improvement to master oscillator with more detectors
and phase shifters

u Upgrade merger beamline after two guns with 2 pulsed bends, 3 quads, 2 bpms and a new chamberu Installation of 4 pulsed steering magnets and 4 bpms inside of positron capturing sectionu Replacement of flux-concentrator and nominal operational field (12 kA)

Injector linac status and energy

K.Furukawa, Nov.2020

5Injector linac operation

u machine study time this season up to now was devoted to bt beam study andradiation safety
u limited chance to condition and to tune injector beams for 3 weeks
u needs at least half shift per week for rf gun
u more quantitative procedure to stabilize injection beams
Injector linac status and energy

K.Furukawa, Nov.2020

6

Higher energy injection and collisionu Mitigation of accelerator structure failuresv Originally designed for 8 MeV/m, but used at 20 MeV/mv Degradation that lead to high field emission rate and discharges
v Water leaks
v Not only Y(6S) but even Y(4S) could be sufferedu 4-year plan to fabricate and install new accelerator structures

Injector linac status and energy

K.Furukawa, Nov.2020

7

Accelerator structuresu First batch acceptanceof structures (4)u Now being high-powerconditioned
u It exceeded ourexpectations

Injector linac status and energy

K.Furukawa, Nov.2020

8EnergyuRecent effort to optimize parametersv10.753 + 0.023/2 GeV could be possible with backups³ e+ : 4.071 GeV, e- : 7.124 GeV³ with 2 nC/bunchuAfter structure upgrade in 2023 winterv6S : 11.020 GeV could be reached with backups³ e+ : 4.165 GeV, e- : 7.289 GeV³ with 2-3 nC/bunchuBT limit³ e+ : 4.290 GeV, e- : 8.465 GeV (both coil heating limit)uMR
vNo discussion yet, while included in the designvEasier with Belle II solenoid scaled
vOtherwise, …
Injector linac status and energy

K.Furukawa, Nov.20209

Thanks

Injector linac status and energy

K.Furukawa, Nov.2020

10

Linac Beam Property Requirements

Linac Beam Parameters for KEKB/SuperKEKB
Stage

KEKB (final)

Beam
EnergyStoredcurrent
Life time(min.)e+e–e+e–e+e–e+e–e+e–

3.5 GeV

8.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

1.6 A

1.1 A

1.0 A

1.0 A

––

1.8 A

1.3 A

3.6 A

2.6 A

150

200

100

100––––66

primary e- 10

Bunchcharge (nC)
Norm.
Emittance

1→ 0.4

Simultaneous top-up
injection
(PPM)

0.5

1200/401400

Phase-III (interim)

310

1000

Phase-III (final)

primary e- 10130(gbe) (mrad)
EnergyspreadBunch /Pulse
Repetition
rate

Phase-II (achieved)

primary e- 8

1→1

Phase-I (achieved)224

150/30100/40100/1540/20(Hor./Ver.)(Hor./Ver.)(Hor./Ver.)(Hor./Ver.)→4150(Hor./Ver.)

0.13%

0.13%

0.50%

0.50%

0.16%

0.10%

0.16%

0.10%

0.16%

0.07%

222222222

250 Hz

25 Hz

25 Hz

3 rings(LER, HER, PF)

No top-up

Partially

50 Hz

50 Hz

4+1 rings (LER, HER, DR, 4+1 rings (LER, HER, DR,PF, PF-AR)
PF, PF-AR)

u Final parameters will be updated
Injector linac status and energy

K.Furukawa, Nov.202011