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Feedback On Nanosecond Timescales (FONT):

Philip Burrows

Neven Blaskovic, Douglas Bett, Glenn Christian, Michael Davis, Young Im Kim, Colin Perry

John Adams Institute

Oxford University

IP Feedback

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Outline

• Reminder of CLIC IPFB prototype

• Remarks on L*

• ATF2 IP FB concept

• Results of recent beam runs

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IP beam feedback concept

Last line of defence against relative beam misalignment

Measure vertical position of outgoing beam and hence beam-beam kick angle

Use fast amplifier and kicker to correct vertical position of beam incoming to IR

FONT – Feedback On Nanosecond Timescales

CLIC Final Doublet Region

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CLIC Final Doublet Region

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CLIC Final Doublet Region

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Comments on L*

• Current geometry:

time of flight IP BPM kicker IP ~ 24 ns

• Demonstrated FONT3 electronics latency = 13ns

• Estimated IPFB latency = 37ns

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CLIC IP FB performance

Single random seed of GM C

Resta Lopez

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For noisy sites:

CLIC IP FB performance

factor 2 - 3 improvement

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Comments on L*

• Current CDR geometry:

time of flight IP BPM kicker IP ~ 24 ns

• Demonstrated FONT3 electronics latency = 13ns

• Estimated IPFB latency = 37ns

• In principle, change of L* need not affect IPFB position and latency, but needs to be engineered carefully, considering other beamline components

CLIC Final Doublet Region

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FONT5 installation at ATF2

ATF2 extraction line

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IP kicker IPBPMs

FONT digital

FB

IPBPMelectronics

FONTamplifier

e-

ATF2 IP FB loop scheme

Eventual goal is to stabilise the small ATF2 beam (design 37nm)at the nanometer level

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Nanometer beam FB at ATF2 IP

• Much harder than IPFB at ILC or CLIC!

• Only 1 beam must measure beam position directly

• nm-level stabilisation requires nm-level position meas.

Cavity BPMs (rather than striplines)

• Cavities intrinsically slow, signal processing complicated

• Cavities required to resolve 2 bunches within << 300ns

Low-Q cavities and low-latency signal processing

New BPMs+electronics (KNU), new IP chamber (LAL)

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Layout with new IP kicker

Designed by Oxford

Fabricationarrangedby KEK

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IP kicker IPBPMs

FONT digital

FB

IPBPMelectronics

FONTamplifier

e-

Preparatory tests June 2013

Existing IPBPMs

Honda low-latency electronics

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Preparatory test setup

A B

Preparatory test IPFB loop

Analogue Front-end

BPM processor

FPGA-based digital processor

Kicker drive amplifier

Strip-line kicker

Beam

Cavity BPM

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IP Feedback Results

FB Off Jitter: 170 ± 10 nmFB On Jitter: 93 ± 4 nm

FB Off Correlation: 81%

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IP Feedback Results

FB Off Jitter: 170 ± 10 nmFB On Jitter: 93 ± 4 nm

FB Off Correlation: 81%

FB On Correlation: -16%20

Incoming Beam Position Scan

10 μm pos. scan

Bunch 2

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IP BPM resolution

• Beam size during measurements ~ 100 nm

• Model beam jitter ~ 20% of beam size, i.e. 20nm

• Assuming results are resolution limited …

• Resolution = 93 nm / sqrt(2) ~ 65 nm

(no direct resolution measurement possible)

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New IP chamber installed summer 2013

Commissioning Started November:alignment, BPM signals

11cm Low-Q IP-BPM design

11cm Low-Q IP-BPM drawings of HFSS

100mm

100mm

Sensor cavity

Wave guideAntenna

Designed frequencyX-port: 5.712 GHzY-port: 6.426 GHz

Full size : 11cmx11cm (to

install IP-Chamber)Light weight:

1 kg (Single cavity)2 kg (Double cavity)

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In May tests resumed w. Honda electronics

FF quad current scan to set vertical beam waist at IPB

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In May tests resumed w. Honda electronics

Centre beam in BPM using mover optimise resolution

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In May tests resumed w. Honda electronics

Centre beam in BPM using mover optimise resolution

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Summary

• ATF2 IPFB prototype is progressing

• Beam stabilised (June 2013) to ~ 100nm level

• Beam jitters measured (June 2014) ~ 60nm (best)

• Beam studies continue until June 20th

• Attempting to disentangle jitter/resolution

• Looking at boosting signal levels resolution

• Hope to close FB loop with improved resolution