BPAC November 2020

Injector linac status

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

K.Furukawa, Nov.2020

1

Improvements during summer shutdown
u Installation of diffractive optical element (DOE, laser profile shaping),
laser position stabilization feedback, cathode,etc. for true 50 Hz, cleaning and stabilizationu Improvement to master oscillator with more
detectors and phase shifters
u Upgrade the merger beamline of two guns with 2 pulsed
bends, 3 quads, 2 bpms and a chamber for true 50 Hz
u Installation of 4 steering magnets and 4 bpms inside of
positron capturing sectionu Replacement of flux-concentrator and nominal operational field (12 kA)
u And many other improvements

Injector linac status

K.Furukawa, Nov.20202

primarycharge (nC)

Positron yield

Y. Enomoto

8.4

Flux concentrator
replacement

8.2
8.0
7.8
7.6
0.6

After summer

positron yeild

0.5
15_T (2020/7/2)
simulation @ 16_5
16_5 (2020/7/2)
16_5 (2020/10/09)

0.4 Before summer
0.3
0.2
0.1
0.0

02468101214

FC current (kA)
Injector linac status

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
uuuuu

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

Injector linac status

K.Furukawa, Nov.2020

4

Injector linac operation
u HER

u LER

u PF ringu PF-ARu Injector linac could not allocate machine study time this season up to last week,that was devoted to bt beam study and radiation safety.
u Injector linac had limited chance to tune injector beams as we shared startup
time for light sources, who cancelled most of beam time before summer.
u This week, several study items are being performed.
Injector linac status

K.Furukawa, Nov.2020

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Investigations and improvements in this weeku Discrete vertical orbit³ Discrete orbits observed with light-source injections, that didn’t affect the injection much (?)

v Caused by the combination of magnetic aftereffect and hysteresis of the new pulsed
bending magnet to merge two guns, and by the beam pattern (found on Nov.18)
v Would tune the beam pattern in this season³ Further tuning measures during winter shutdown

u 7-minute orbit variation³ Orbit and charge variation even with laser stabilization, that annoyed the injection tuning.

v Caused by one of the chillers for a optical table (found on Nov.19)
v Would stop it for the moment, while laser position stabilization should cover this
³ Further investigation in this week

u Emittance break-up at the latter part of the beam transport³ Emittance blow-up several times while the beam goes through BT

v Precise tuning of the beam with new beam monitors like OTR beam profile, etc
v Trying to understand step by step from beam experiments and simulations

u Many other items like dispersion corrections, device calibrations,
backup device preparation, operation software improvements, etc.
Injector linac status

K.Furukawa, Nov.2020

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Examples at the end of linac
After summer

Before Summer

Y. Seimiya

After SummerHor.

* 7-minute instability==>
Chiller for a table

Ver.
Charge* Discrete verticalorbit==>
New pulsed bend

Injector linac status

K.Furukawa, Nov.2020

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Emittance break-up in BTe+X

N. IidaMeasured by WS● Emittance due to Jitterー Emittance due to BPM res.
ー Emittance due to sde- X●21/Oct
22/Oct(invisibly small)Same emittance lineof BT2 as BT1
Required emittancefrom LER/HERe+Y•e- Y

21/Oct•22/Oct•Injector linac status

The horizontal orbit jitterin the e+ is negligiblysmall.
The other jitter
emittances at BT1 iscomparable as measuredemittance.
But in BT2, all measured
emittances are larger
than the jitter emittances.

K.Furukawa, Nov.2020

早朝
11/18
（水）

日中 LINAC mode

準夜 BT dump mode２値化問題(パターンを変える。)(夏井)~18:00OTR, BT2 QuadScreen

11/19
（木）

QuadBPM(BTp)
OctoPos(SY3)e- datataking

7分変動の調査(吉田)KBP DS Study(三浦)~できるまでBT Study

11/20
（金）

KBP DC4 response
8:00~9:00e-放射線測定
25Hz
Jarc dispersion(吉田)Jarc dispersion(清宮)3-5 sector 軌道FB(清宮)~できるまでBT Study

11/21
（土）

TBD

KBE beam
Cleaning~18:00Conditioning
KBP DS Study(三浦) 1H
MOFB Offの影響を見る

11/22
（日）

KBE beam

Conditioning

KBE beam
Conditioning

KBE beam
Conditioning

11/23
（月）

KBE beam
1st laser

KBE beam
1st +2nd laser

KBE beam

11/24（火）KBE beam

HER injection
LER injection

Injector linac status

K.Furukawa, Nov.2020

u Many improvements during summer shutdown and additional itemsin this weeku Injection stabilization is still one of the major challenges for now
u Further stabilization expected with existent hardware to help
investigation at the beam transport line
u Then, pursue several more steps to final designed beams

Thank youInjector linac status

K.Furukawa, Nov.202010

e- beam V-orbit binarization at LINAC end

Injector linac status

K.Furukawa, Nov.202011

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

K.Furukawa, Nov.2020

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

Injector linac status

K.Furukawa, Nov.2020

13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

K.Furukawa, Nov.2020

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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)

0.51200/401400

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

K.Furukawa, Nov.202015

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

K.Furukawa, Nov.2020

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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

K.Furukawa, Nov.202017