C/S-band cavity BPMs

A. Aryshev (KEK), S. T. Boogert (JAI@RHUL), G. Boorman, F. Cullinan, J. Frisch, A. Heo, Y. Honda, J.Y. Huang, S.J. Hwang, N. Joshi, E-S Kim, Y. I. Kim, A. Lyapin, D. McCormick, S.

Molloy, J. Nelson, Y.J. Park, S.J. Park,T. Smith,T. Tauchi, N. Terunuma, G. White.

SLAC, KNU, PAL, KEK, JAI-RHUL, KEK, ATFhttps://www.pp.rhul.ac.uk/twiki/bin/view/JAI/BeamPosition

Summary of progress•C-band

•Normal resolution with 20 dB 200 nm

•Best resolution recorded, 20 nm

•S-band

•About 1 um (with 15 dB loss in cable)

•Unstable when DR-RF ramp is on

•IP

•Commissioning phase

•Y resolution ~100 nm (needs good IP steering)

•Write paper on Hardware and initial results (YI Kim, Lyapin, Boogert)

Introduction• Earthquake damage : relatively light

• Main change to network : made old VME controllers inoperative, unable to boot

• Hardware

• Exchanged : MVME167 to MVME3100

• Integration of SLAC 16-bit digitisers

• Software upgrades : Over 40 large upgrades

• Automatic EDM

• Each polarisation has own reference, displays, processing, DAQ, etc

• Measurements and checks

• 714, C-band, S-band LO and CAL

• Digitiser noise spectra

• Analysis

• Calibration scale errors

• Multi-bunch

Hardware changes in detail•Exchanged : MVME167 to MVME3100

•Integration of SLAC 16-bit digitisers

•C-band CAL tone broken

•S-band sources, rationalised and checked

•S-band cables, reorganised due to new IP region shield penetration

•Checked out Zygo straightness monitor system

SLAC digitisers•16 bit

•4 channels

•120 MHz internal clock

•Excellent linearity

•Problem in impedance

•Appears to be 1 MOhm

SLAC+SIS digitizers•Fully integrated

•6 SLAC ADC cards

•4 channel

•16 Bit

•Bipolar

•High linearity

•Low phase noise (internal clock)

•Impedance issue....

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are needed to see this picture.

SLAC impedance check

•IPY1 : Inserted

SLAC digitiser impedance•Diagnostic check list

•Checked with multimeter (DC measurement)

•Triggered 25 MHz source

•Scope test at 50 Ohms

•Signal looks like it has no reflections

•Can be avoided in software even for references which have large Q compared with IPBPMs

Check TOMORROW

C-band RF distribution•714 Input into RF

locking box, generates

•100 MHz digitiser clock

•LO

•LO has some sidebands

•Should check at down mixer electronics in tunnel

•Large amplification 5W

C-band cal tone•Only visible damage

due to quake

•Temperature interlock for C-band CAL tone 5W amplifier

•Fixed!

•Need to check CAL tone to

•MPIP (done!)

S-band system digitiser•New MVME-3100

•2 8-Channel SIS modules, enough for S-band system

•Clock and trigger still maybe an issue

•DR-RF on!!!!!!

•Propose to internally clock as have spare channels for multiple references now (IP BPMs moved to SLAC digitisers)

Install TODAY

S-band signal cables•Cut down cables

•Length reduced by approximately 20 m

•Attenuation similarly reduced

•Need for hybrids/amplifiers probably gone

•Will install hybrids

BPMOld attn

(dB)New attn

(db)SF1FFx 14.9SF1FFy 14.4QF1FFx 14.5QF1FFy 14.9SD0FFx 14.6SD0FFy

14.7

QD0FFx 14.7QD0FFy 14.8REFS1 14.8

Measure TODAY

S-band sources•8 and 20 GHz

Hittite sources

•LO and CAL tones

•Source power and frequency stability not such an issue but spectrum is important

•Need to propagate effect to down-converted signals

LO2kHz span

CAL8GHz 2 MHz span

S-band RF distribution•At mixdown

electronics

•LO looks reasonable

•Completely unlocked from 714 MHz of ATF, why is there such a coherent change in BPM performance (IQ rotation) when DR-RF ramp is switched on

Zygo straightness system•Email from Mike

Hildreth

•Check

•Laser (ok)

•VME system (ok-ish)

•Computers (ok)

•Laser path needs realignment

•Preparing for August planned trip by Mike H.

Software changes in detail•Main change use to IP region BPMs

•Previously code used one reference cavity per dipole PAIR

•Totally automatic system configuration

•Generates all files (displays included from one master control file)

•More stable database, rarely have to change main DB configuration even if hardware changes drastically

•Complete system configuration in database

•Determine how the BPM system is operating, what is connected, how it is being processed

Automation•Completely automatic configuration. Edit signal file and all

settings down to hardware, analysis and display changed

Digitiser noise• Two types of digitiser

• Need to understand the effect of digitiser noise on BPM processing

• Two types of investigation

• Calibration tone (fit to sine wave)

• Data taken but need to process

• Beam off

• Done, results on right

BPMDigitise

rNoise [ADU]

QD10Xx rawSIS (14

bit) 2.53

QD10Xx proSIS (14

bit)0.12

IPAx raw SLAC (16 bit)

7.44 (/4=1.86)

IPAx pro SLAC (16 bit)

0.72 (/4=0.18)

Frequency shifts•In normal

operation often notice temperature shifts

•Appear as linear phase in down-mixed signal

•Temperature changes cavity size, hence frequency

•Need to temperature monitor entire BPM system? Possible? Resolution?

Basic : -112 kHz/KBeam pipe-50-60 kHz/K

t0 resolution•Beam arrival time (t0)

•Substantial jitter and then longer term drifts

•Phase correction algorithms depend on this number

•Measured in REFC1 diode detector

•Linear fit to rising edge of signal

•Better method?

Charge [10^10] t0 RMS [ps]0.3 6020.5 1600.8 331.0 32

0.3 x 10^10 e-

Calibration Errors due to Slow Orbit Drift and Random Beam Jitter

•Record ~1000 pulses of position measurements

•Smooth using moving average with flat window of length equal to calibration step length in pulses

•Fit points separated by window length against positions in calibration scan to determine fractional error on position scale

•Subtract smoothed signal to leave random jitter

•Calculate random errors analytically

•Subtract jitter for BPMs on movers then repeat analysis

Frankie Cullinan

Results

S/m

Frankie Cullinan

23

IQ : Without bunch subtractionIQ : Without bunch subtraction

BunchNo

φ (rad)

|Δφ | (rad)

1 0.98778

2 0.32898 0.65883

3 -0.59777 0.92671

Rotation Angle:

o BPM is moved along Y axis at 200, 100, 0, 0μm positions respectively.

o I & Q are calculated in a similar way as single bunch calibration, without any bunch subtraction.

o With change in mover position, I&Q from 1st bunch moves along a straight line in IQ plane passing through (0,0)

o Steps along straight lines in IQ plane from 2nd and 3rd bunches shows the behaviour expected from a cavity BPM.

o IQ signal from a bunch is polluted by the decayed signal from previous bunches.

Nirav Joshi

24

IQ : After bunch subtractionIQ : After bunch subtraction

BunchNo

φ (rad)

|Δφ | (rad)

1 0.98778

2 -0.04182 1.029609

3 -0.96794 0.926120

Rotation Angle:

Bunch Subtraction:

oi & q signals from BPM and reference cavities are subtracted separately before normalization.

oDecayed i & q from previous bunch is subtracted from current bunch.

oSubtracted signal is then normalized.

oPhase difference between bunches becomes even.

Nirav Joshi

Future work•Cavity temperature monitoring

•Monitor temperature by frequency drift

•Ok for a phase detector but not dipole system

•Consider installing temperature monitoring on all BPMs

•Resolution of current system?

•High charge operation (question from Terunuma-san)

•Dipole saturation is always a problem

•Reference saturation is not an option (should not happen)

•Ordering 5 remote controlled C-band attenuators

•Understand entire BPM system error budget, statisical and systematic errors etc.

Summary•System is working well,

compared to pre-earthquake situation

•Many cases improved

•Significant software changes

•Expect some bugs, tried to remove most of them

•Improved maintainability

•Continue with pre-quake program

•Attempt to get high resolution operation for >1 week without calibration