Beam Monitors DR/MR
The 22nd KEKB Accelerator Review Committee
2018/3/14
Ikeda, Arinaga, Ishii, Iwabuchi, Tejima, Tobiyama, Fukuma,Flanagan, MoriIntroduction
SystemQuantity
HERLERDR

Beam position monitor (BPM)

465

444

83

Displacement sensor

110

108

0

Transverse bunch feedback system (FB)

22

1

Longitudinal bunch feedback system (LFB)

(1)

10

Visible SR size monitor (SRM)

1

1

1

X-ray size monitor (XRM)

1

10

Beamstrahlung monitor (LABM)

110

Betatron tune monitor

111

Beam loss monitor (LM)

184

DCCT

111CT11(1)*Bunch current monitor

110IP-FB

11034*substitution equipment

DR208• Sensor : Button electrode with φ6mm.
• Chamber : Two button electrodes areattached to one flange.
• Detector:

φ6φ89024BPM (1)BPM monitor chamber– Digitex 18K11 Log-ratio detector (VME 1W)• Memory 32k word/ch– Memory size too large, limit the length down to 2k/ch
by software» Due to slow CPU power of VME IOC.
Digitex 18K11

BPM (2)• Timing:– Wideband band pass filter (Center 504 MHzBW~24 MHz), needed to adjust the cable delay
within 4 ns.
– Universal frequency divider (1/230 for DR) withexternal synchronization function using ZYNQFPGA.
– 32 ch digital delay (508MHz) using ZYNQ FPGA.
• Adjust the delay with 2 ns step for each
modules (21 / rack).

BPM (3)• Before commissioning:– Measured the cable length from BPM panel in the tunnel to the BPM station
using Network Analyzer-based TDR (E5071C) and adjusted them withinO(mm).– the measured standard deviation was around 30 ps with typicalcable length of 30 m.
– Survey with FARO 3D-ARM and preset offset in EPICS database.
1.100
1.000
0.900
0.800
0.700
0.600
0.500
0.400
0.300
0.200
0.100
0.000
-0.100-0.200-0.300-0.400-0.500-0.600-0.700-0.800-0.900-1.000-1.100

BPM survey

ΔX(mm)

0.600
0.500
0.400
0.300
0.200
0.100
0.000
-0.100-0.200-0.300-0.400-0.500-0.600-0.700-0.800-0.900-1.000-1.100-1.200-1.300-1.400-1.500-1.600Survey results

ΔY(mm)

BPM (4)• Before first turn:

12,80013,00012,70012,50012,60012,000Amp(0p)

ADC counts– Measured the response of detector (18k11) to clock pulse at a test bench, and foundthat the best timing of a beam from falling edge of the clock is 369ns.
– Measured the clock timing with a broadband oscilloscope as trigger by an incident
beam in first BPM of each BPM station and set each delay.

12,50012,40011,50011,00012,30010,50012,20010,00012,100
-10

9,500

-50
Delay(ns)

5

10100

110

120
Delay

130

140

BPM (5)• Status:– All BPMs are workingwell.

FB (1)• Damp the residualbunch oscillation
at injection orextraction.
• Digital filter : iGp12
with firmware
matched with DR• Power amp :250W x 4 (reuse ofKEKB)Monitor chamber

iGp12 feedback processor

Transverse strip-line kicker

bunch detectorFB (2)• Status– Roughly adjusted the phase shift of iGp12 processors for bothhorizontal and vertical planes.
– Successfully excited betatron oscillation with stable amplitude
using single-bunch PLL excitation function of iGp12.
– Tek RSA306 real time spectrum analyzer to observe spectrum(using VNC connection from CCR).

Bunch current monitor• System:• Detection circuit(same as used in MR)• VME board (Digitex18K10)• Status:• Working well.

Betatron tune measurement system• System• Down-convert the tracking generator
output of the spectrum analyzer, anddrive beam.
• Observe the electrode output
directly with spectrum analyzer.
• Status:• Tune measurement system isworking well.

SRM(1)

Layout in the DR SRM hut
Streak camera line
gate camera line

• Source bending magnet :– Bending radius of 3.14m– Just after extraction line

Extraction chamber• Extraction mirror : Be(Recycled from KEKB MR)• Detector:– Streak camera, gate camera• Status:– Completed alignment of light path and adjustment of camera.
– Data acquisition of damping beam size and length.

SRM (2)Streak camera measurement
Bunch shape of just after
injection is not clear andcould not decide the bunch
length, but the shape issimilar to calculated one.

(Simulated by N.Iida)SRM(3)• 5ms• 10ms• 200msSRM(4)• Bunch length– Damped around 20msec after injection.
– Absolute value is near the design value (6.5mm).

1st turnSRM(5)

1st turn
50μs• Transverse beam shape– Measured single shot for each turn bygate camera.
– Damped shape is observed.
• The quantitative analysis was difficult since
light intensity was not enough and could
not use BPF for measurement.

– Measure again with higher bunch
current.

150μs
450μｓ
1ms
5ms
10ms
20ms
50ms
200ms

LM
• Purpose– Used for commissioning, injection tuning and monitoring in routine
operation.
– Abnormal beam loss stops the injection to the ring.

• Specification:– Calculated beam loss

• 2.5% @ injection point.
• 2.7% @ arc sections.
• 20% @collimator.

• Sensor : Ion chamber (9 m FC-20D co-axial cable)– Covers all of the tunnel.
– Recycled from linac– Sensitive down to the loss of around 0.1mA/s• Readout : Integrator (0.1,0.3,1ms) and amplifier(×1,10,100,1000)• Status:– Working well.
– I/L threshold set to 2V since extraction septum trouble caused higher
beam loss near SRM hut.
– Raise I/L level, after checking the radiation level at the beam loss.

Ion chamber on tunnel wall

DCCT•••••

Specification:＜200mA, σ=30µA
Chamber : Octagonal ceramic chamber + Core (Recycled from MR).
Readout：Modification for DR.
Take the current data continuously at about 5ksps using Keysight 34465A DMM.
Status:– Current measurement working well.
– Chamber direction was reversed w.r.t. e+, and corrected by software.
– Injection stop when the current exceed threshold (17mA).

DCCT Chamber

Ceramic chamberCoreMRBPM• Added 22 gated turn-by-turn monitor units mainly around IRand injection points– In total, 139 units have been installed.

FB• Replaced 4 x AR250A250 amplifiers for LER transverse FB with
R+K CA010K251-5757R 500W x 4 amplifiers.
– Much better time response, higher power.

• Replaced damaged high power attenuators (1.5kW)– HER :1
– LER longitudinal : 1• Replaced water chiller system for LER longitudinal kickers.
– Much better reliability, higher cooling power.

• Heating of amplifiers room (~35 C Fuji B4)– need much higher
cooling power. Replacement of air-conditioners is planned.

BPM detector and feedback controller
for vertical collision feedback

down converter(analogue)• Specification:– BPM position resolution < 1 μm (with > 500mA)– Repetition of feedback 5kHz to 32kHz– Feedback bandwidth 100Hz• BPM detector:– Analog down converter followed by digital LPF

BPM digital LPF
feedback processor• Feedback controller:– Feedback processor and Corrector controller– Conforming to μTCA specification• Status:– The detector was tested in Phase 1 operation.
– All devices already have been installed in Tsukuba control room.

Corrector controller

XRM• Made Helium enclosure in detector box to minimize scattering and ozone production.
• Changed Be filters in LER and HER to much thinner ones to eliminate suspected source ofimage smearing due to scattering (LER: 500μm→200μm, HER:16mm→200μm).
• Changed HER masks to re-optimize for softer X-ray spectrum as a result of changing Be filters.
• Developed readout software for vacuum gauge controller and reader.

SRM• Investigated magnification of system which was
higher than expected.

– Injected a laser beam from source point to measure slit
ratio, and concluded that extraction mirror caused theeffect.

• New wider mirrors to increase light intensity atstreak cameras.
• Examined streak camera and then founddegradation of streak tube.
– Will be replaced in future.

LM• Added 31ch IC to cover all of the ring.
• Attached PIN PD’s to 6 new collimators.

SummaryDR• All monitors are working well without any serious problem.
• All monitors can measure normally.
• Tune up further more with a progress of phase-II
commissioning.
MR• Ready for the Phase-II commissioning.

32ch digital delay

IP FBBunch Length @ DR
• σz=6.5mm

by simulation

2012/2/21 The 17th KEKB Accelerator Review Committee

Streak camera measurement• 1st turn (integration of100 turns.)• 1ms after
injection(integrationof 100 turns)

Streak camera measurement• 2ms after(integrationof 100 turns.)

Dithering interface

D4 HER

window
Extraction mirror

21m

1st mirror

Source point

1.5m

3st mirror

9.5m