1 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

2 Outline Reminder of IP FB prototypes (ILC + CLIC) ATF2 IP FB concept Results of recent beam runs Summary + outlook

3 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

4 KickerBPM 1 Digital feedback Analogue BPM processor Drive amplifier BPM 2 BPM 3 e- ILC prototype: FONT4 at KEK/ATF

5 KickerBPM 1 Digital feedback Analogue BPM processor Drive amplifier BPM 2 BPM 3 e- ILC prototype: FONT4 at KEK/ATF

6 KickerBPM 1 Digital feedback Analogue BPM processor Drive amplifier BPM 2 BPM 3 e- ILC prototype: FONT4 at KEK/ATF BPM resolution < 1um Latency ~ 130ns Drive power > ILC

7 KickerBPM 1 Analogue BPM processor BPM 2 BPM 3 e- CLIC prototype: FONT3 at KEK/ATF

8 KickerBPM 1 Analogue BPM processor BPM 2 BPM 3 e- CLIC prototype: FONT3 at KEK/ATF Electronics latency ~ 13ns Drive power > CLIC

CLIC Final Doublet Region 9

10

CLIC Final Doublet Region 11

12 CLIC IP FB performance Single random seed of GM C Resta Lopez

13 For noisy sites: CLIC IP FB performance  factor improvement

FONT5 installation at ATF2 ATF2 extraction line 14

15 IP kickerIPBPMs FONT digital FB IPBPM electronics FONT amplifier e- ATF2 IP FB loop scheme Eventual goal is to stabilise the small ATF2 beam (design 37nm) at the nanometer level

16 Layout with new IP kicker Designed by Oxford Fabrication arranged by KEK Installed May 2012

17 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)

18 IP kickerIPBPMs FONT digital FB IPBPM electronics FONT amplifier e- Tests started November 2013 New IP chamber installed Summer 2013 New IPBPM electronics developed by KNU, designed for few nm resolution

In vacuum IP-BPMs and piezo movers BPM A&B BPM C Piezo Movers (PI) Piezo Movers (Cedrat) BPMs – Bolted aluminum plates, no brazing because of In- vacuum. – BPM A&B bolted together. – BPM C is independent. Piezo mover – BPM units are mounted on the base with three piezo movers. – Dynamic range of each mover is +/- 150 um. IP Slide from Terunuma Initial alignment need to be better than this. Commissioning now under way: Alignment, BPM signals, resolution …

20 IP kickerIPBPMs FONT digital FB IPBPM electronics FONT amplifier e- Preparatory tests June 2013 Existing IPBPMs Honda low-latency electronics

21 New kicker A B

FONT5 operation at ATF2 22 Aim to stabilise beam in IP region using 2-bunch spill: 1. Upstream FB: monitor beam at IP 2. Feed-forward from upstream BPMs  IP kicker 3. Local IP FB using IPBPM signal and IP kicker 22

Upstream FONT5 System Analogue Front-end BPM processor FPGA-based digital processor Kicker drive amplifier Stripline BPM with mover system Strip-line kicker Beam BPM Resolution < 350nm Dynamic range of the BPM system+/-500μm System Latency<150 ns Amplifier Bandwidth~30 MHz 23

Stripline BPM resolution ATF2 stripline BPMs: single-pass beam, bunch Q ~ 1 nC 330 nm rms

Interaction Point FONT System Analogue Front-end BPM processor FPGA-based digital processor Kicker drive amplifier Strip-line kicker Beam Cavity BPM 25

26 IP FB latency measurement Latency ~ 160ns

27 Test programme Preparations for beam stability in IP region with 2-bunch beam, bunch separation 270ns: 1. Readout of IPBPMs with 2-bunch beam 2. Upstream FONT FB: record beam in IPBPMs 3. Feed-forward from upstream FONT BPMs  IP kicker: record beam in IPBPMs 4. IP FB using IPBPM signal and IP kicker Standard procedure is to correct beam in y at IPB

Upstream FB (Measured at IPB) FB Off Jitter: 0.35 ± 0.02 μm FB On Jitter: 0.30 ± 0.01 μm FB Off Correlation: 79% 28

Upstream FB (Measured at IPB) FB Off Jitter: 0.35 ± 0.02 μm FB On Jitter: 0.30 ± 0.01 μm FB Off Correlation: 79% FB On Correlation: 14% 29

Feedforward Results FF Off Jitter: 160 ± 10 nm FF On Jitter: 106 ± 10 nm FF Off Correlation: 73% 30

Feedforward Results FF Off Jitter: 160 ± 10 nm FF On Jitter: 106 ± 10 nm FF Off Correlation: 73% FF On Correlation: 23% 31

Incoming Beam Position Scan Bunch 2 6 μm pos. scan

IP Feedback Results FB Off Jitter: 170 ± 10 nm FB On Jitter: 93 ± 4 nm FB Off Correlation: 81% 33

IP Feedback Results FB Off Jitter: 170 ± 10 nm FB On Jitter: 93 ± 4 nm FB Off Correlation: 81% FB On Correlation: -16% 34

Incoming Beam Position Scan 10 μm pos. scan Bunch 2

ATF2 beam stabilisation results 1.Upstream FB: beam stabilised at IP to ~ 300 nm 2. Feed-forward: beam stabilised at IP to ~ 106 nm 3. IP FB: beam stabilised at IP to ~ 93 nm Getting interesting! (i.e. hard) 36

37 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)

38 IP correction test programme Preparations for beam stability in IP region with 2-bunch beam: 1. Readout of IPBPMs with 2-bunch beam 2. Upstream FONT FB: record beam in IPBPMs 3. Feed-forward from upstream FONT BPMs  IP kicker: record beam in IPBPMs 4. IP FB using IPBPM signal and IP kicker  ready for tests with high-resolution IPBPMs

Beam Stabilization at ATF-EXT ー Intra-train Fast Feedback ー expected (from results in EXT ） FB OFF: jitter 14.7 nm FB ON: jitter 2.6 nm EXT-FONT by stripline BPM, result 2014/Jan - latency ~133 ns ? IP-FONT by IP Cavity BPM FONT feedback Slide from Terunuma FONT group, slide from Terunuma

Beam Waist Scan Through IPB