Upgrade of BPM DAQ System for SuperKEKB Injector Linac
M. Satoh, F. Miyahara, T. Suwada, and K. Furukawa
THPPC033
Accelerator Laboratory, KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801, JapanT. Kudou and S. Kusano
Mitsubishi Electric System & Service Co., Ltd, 2-8-8 Umezono, Tsukuba, Ibaraki 305-0045, Japan
SuperKEKB Injector Linac

Current BPM DAQ System

Data acquisition speed (Hz)ySimultaneous injection for 4 independent rings(SKB e-/e+, PF, and PF-AR) w/ different beam energies.
yIncrease positron beam intensity:
y 1 => 4 nC/bunchyIncrease electron beam intensity and Reduce electron beam emittancew/o Damping ring:y 1 nC => 5 nC
y 100 mmmrad => 20 mmmrad
yHigh precision beam position measurement and control ( d 10 Pm )350

ch1ch2ch3ch4

300
250200150100500050 100 150 200 250 300 350 400 450 500

Waveform length (k-points)

Cable Combiner BOX
FIG. 5: Schematic drawings of current BPM DAQ system. Twenty four systems
process 94 BPMs䠄WindowsXP-based digital oscilloscope).

FIG. 6: Data acquisition speed of current DAQsystem. For the real beam operation, oneoscilloscope processes the waveform of 2000
data points and two channels at the same time
up to 50 Hz.

Vx 䡚26.3 Pm

Vy䡚 25.1 Pm(a) Horoizontal(b) Vertical

FIG. 1: Schematic drawing of SuperKEKB Linac. Colored parts will be newly installed.
TABLE 1: Main parameters of former KEKB and SuperKEKB.
Parameters

KEKB
e+

SuperKEKB
e-e+e-Ring:Energy (GeV)

3.5

847

Stored current(mA)

1.6

1.2

3.6

2.6

Beam lifetime(min.)

150

200

1010

Bunch charge(nC)*1 (10)14 (10)5Emittance(Pmrad)

2100

1001020

Energy spread
(%)

0.125

0.05

0.07

0.08

Bunch length(mm)

2.6

1.3

0.7

1.3

FIG. 7: 3-BPM result of current BPM DAQ system.

New System Candidates

Injector Linac:yVME-based System (KEK Linac).
yLIBERA Single Pass Electron (i-tech).
y 16 bit A/DC with 160 MSa/s.
y SAW filter: fc = 522 MHz, Bandwidth = 24 MHz
y Fast controllable attenuator : 0 dB ~ 31 dB.
y Pulse-to-pulse (50 Hz, 20 ms interval) measurement.
y EPICS IOC ready, Event receiver (MRF compatible) inside.

(*) Numbers inside braces denote the charge of primary electron for positron production.

Performance Evaluation (3-BPM Measurment䠅
Vy䡚 7.06 PmVx 䡚7.05 Pm
FIG. 2: Schematic drawing of beam operation scheme for SuperKEKB Linac.

Low Emittance Electron Beam Injection (w/o damping ring)yComponent misalignment (Accelerating structure, Q-Mag.) causes the serious(a)emittance growth.
ySimulation was conducted for the 500-m-long straight line ( 5 nC, initial emittance 10mmmrad, Misalignment of accelerating structure: ı =0.5 mm).
(a) Horizontal(b) Verticaly Maximum emittance at end of linac (in 100 different seeds of misalignments)
FIG. 9: Results of 3-BPM.
168 mmmrad (FIG. 2.)
Horizontal and vertical beam position measurement(c) After phase matching
precisions are:yA precise initial beam offset and angle control can realize the emittance preservation (b) Before phase matching
FIG. 8: Linac beam orbit along Linac (for PF injection w/ 0.3
Vx ~ 7.05 Pm
11.5 mmmrad instead of 168 mmmrad (FIG. 3.).
nC). (a). Horizontal (upper), vertical (middle) beam orbits, and࣭Precise beam position measurement and control => Crucial issuecharge (bottom). For increasing measurement precision,
Vy ~ 7.06 Pm
200Hx min.

168 mm.mrad

Hx max.

)5-0FIG. 3: Simulation result of emittance growthcaused by the accelerating structure misalignment.

-0.7

1.

s (m)

-1.0
0.50

5' (mrad)

㻏㻡10

600
0-300

FIG. 10: Raw A/DC waveform.

-1200-1500

050

100

150

200

250

Temperature (tunnel)
40
Temperature (gallery)
35

230

125
20

015-1

10-2-3130716 0900

5130717 0900

Temperature (deg.)

Measured position (Pm)Horizontal
Vertical0130718 0900

Date and time (yyMMdd hhmm)

FIG. 14: Results of 2 days measurements(moving average over 5 minutes).

42FIG. 4: Simulation result of emittance growth suppression by
the fine control of beam orbit.

36300t (ns)

0020

40

60

80

100

Att. for #1 bunch (dB)

Evaluation of Long-term stability (variation of gain imbalance)

FIG. 13: Experimental setup.

Att20 x2 (um)Att21 x2 (um)Att22 x2 (um)Att25 x2 (um)Att28 x2 (um)Att31 x2 (um)

8300-9000500

㻏㻠

Ca=1937, Liberae1, PG, 1000, 96.3 ns

1200

-600

0.2
50'x

4000.
75

㻏㻟

0.0-0.2
5-000

300
㻏㻞

0.50

11.5 mm.mrad0)m(m200㻏㻝-0.50.
50-0'x 0100
㻏㻯

1.00
0.75

00
-1.0 .75

㻝㻞㻚㻞㻡
0A/DC counts

40

㻠㻞㻚㻢㻢

25.2

50

575

1500
900

80

0.
00

100

120

0.
2

H nx (mm.mrad

125

0

1st bunch impact on 2nd bunch measurement

160

㻝㻢㻤

150'x2 (Pm)

175

Normalized rms
emittance (mmmrad)signal phases from four strip-lines were precisely adjusted.

Hx averageq = 5 nC, Acc. structure misalignment Vx : 0.5 mm

200FIG. 11: Experimental setup.

FIG. 12: Measurement result. The absolute beam
position of 2nd bunch during changing the Attenuatorsettings in FIG. 11.

Summary and Future Plan
•Toward SuperKEKB Injector Linac Upgrade, we evaluate the performance of theNew BPM DAQ System candidate (LIBERA Single Pass Electron)•The result of 3-BPM measurement shows Vx,y a 7 Pm of measurement
precision.㸦Our goal is less than 10 Pm㸧
•Mass production and install will be conducted after evaluation of anothercandidate (VME-based module).