1. SLAC ESA T-474 ILC BPM energy spectrometer prototype Bino Maiheu University College London on behalf of T-474 bino@hep.ucl.ac.uk Vancouver Linear Collider Workshop '06

2. Introduction : beam energy measurement Vancouver Linear Collider Workshop '06 One of main physics goals of ILC : precision physics e.g. determination of top quark mass Luminosity spectrum and beam energy measurement Systematic uncertainty ! Strive for beam energy measurement accuracy to 10 -4. Stability/calibration : interference with physics data taking minimal Efficiency/cost, ease of operation A magnetic chicane is investigated here... E ~ ∫B.dl/Θ

3. δE/E = 10 -4 δx = 500 nm δx = 500 nm η x : 5 mm α = 0.24 mrad L 1,4 = 3 m L 2,3 = 6 m D 12 = ~ 16 m Length ~ 60 m Current ILC spectrometer design Vancouver Linear Collider Workshop '06 1 23 4 ΔxΔxΔxΔx

4. T-474 test experiment at End Station A Vancouver Linear Collider Workshop '06 Build an energy spectrometer prototype, using a 4 magnet chicane Build an energy spectrometer prototype, using a 4 magnet chicane Goal is to demonstrate the stability of this type of energy measurement at 10 -4 level, and investigate how such a magnetic chicane can be operated most efficiently at the ILC Goal is to demonstrate the stability of this type of energy measurement at 10 -4 level, and investigate how such a magnetic chicane can be operated most efficiently at the ILC Operate at 5 mm η X at center chicane as in ILC design Need ~ 1 µm resolution on position measurement (BPM) With position measurement stability over multiple hours of ~ 100 nm Why ESA ? capable of producing ILC-type bunch capable of producing ILC-type bunch good test bed for systematic studies : vary energy spread, bunch length, beam halo, optics etc... good test bed for systematic studies : vary energy spread, bunch length, beam halo, optics etc...

5. Intended setup of the ESA beamline Vancouver Linear Collider Workshop '06 SPEAR magnets BPM modules 20 m

6. Intended setup of the ESA beamline Vancouver Linear Collider Workshop '06 SPEAR magnets BPM modules In alcove: 2 RF BPM doublets, control steering feedback type: old SLAC RF BPM Old SLAC RF BPM Triplet, each x,y and Q New linac RF BPM prototype Triplet, each x and y (same cavity) Installation : January commissioning run, April first testrun 20 m + interferometer during july testrun (see further)...

7. Commissioning of the ESA beam line Vancouver Linear Collider Workshop '06 January test run 2006 (4 days) : January test run 2006 (4 days) : Commissioning of BPMs 31,32 and 1,2 in ESA alcove Readout, processing software etc... April run 2006 ( 2 weeks ) : April run 2006 ( 2 weeks ) : Commissioning of new ILC prototype linac triplet (BPM 3,4,5) BPM4 on x,y mover system Commissioning of old SLAC BPMs (9, 10, 11) Digitisation optimisation (external/internal clocking) Optimisation of signal processing July run 2006 (2 weeks ) : July run 2006 (2 weeks ) : Commissioning of Zygo interferometer system (BPMs 3,4,5) Further optimisation of hardware (down mixing) Stability data taking with 10 BPMs, frequent calibrations......

8. BPM systems used in current setup Vancouver Linear Collider Workshop '06 SLAC linac style stations Q XY Rectangular cavities, Q, x and y Rectangular cavities, Q, x and y 2.856 Ghz, high Q ~ 3000 2.856 Ghz, high Q ~ 3000 20 mm aperture (0.8 “) 20 mm aperture (0.8 “) C. Adolphsen, Z. Li C. Adolphsen, Z. Li ILC linac prototype cavities ILC linac prototype cavities 36 mm aperture, 2.859 Ghz 36 mm aperture, 2.859 Ghz low Q (~ 500) low Q (~ 500) good monopole suppression good monopole suppression Talk by Zenghai Li Talk by Zenghai Li

9. BPM signal handling Vancouver Linear Collider Workshop '06 BPM 2.856 GHz LO 2.939 GHz 83 Mhz signal SIS3301ADC DDC : phase & amplitude 119 Mhz ext. clock Multiply signal in software by e iωt Multiply signal in software by e iωt Apply gaussian filter to get rid of 2ω component Apply gaussian filter to get rid of 2ω component Sample at fixed point (t0Ref) to preserve linearity Sample at fixed point (t0Ref) to preserve linearity

10. DDC optimisation Vancouver Linear Collider Workshop '06 Determine waveform frequency for DDC by requiring flat phase dependence across downconverted waveform Determine waveform frequency for DDC by requiring flat phase dependence across downconverted waveform Optimise filter bandwidth to get rid of 2 ω component and get best resolution Optimise filter bandwidth to get rid of 2 ω component and get best resolution Optimise sampling point (t0Ref) to have optimal resolution/saturation Optimise sampling point (t0Ref) to have optimal resolution/saturation Old BPMs

11. DDC optimisation Vancouver Linear Collider Workshop '06 Determine waveform frequency for DDC by requiring flat phase dependence across downconverted waveform Determine waveform frequency for DDC by requiring flat phase dependence across downconverted waveform Optimise filter bandwidth to get rid of 2 ω component and get best resolution Optimise filter bandwidth to get rid of 2 ω component and get best resolution Optimise sampling point (t0Ref) to have optimal resolution/saturation Optimise sampling point (t0Ref) to have optimal resolution/saturation Prototype BPMs

12. BPM Calibration Vancouver Linear Collider Workshop '06 How do we go from Amplitude and Phase to Position and Tilt ? Determine I and Q and phase : normalise to reference cavity ( monopole signal ) Get position scale Using corrector scan : Be carefull with saturation at large offsets IQ phase jitter

13. BPM Calibration Vancouver Linear Collider Workshop '06 BPM4 equipped with mover in x,y : correct scale from corrector calibration Check calibration of mover with interferometer Most precise, but only BPM4

14. Resolution, stability over 30 min Vancouver Linear Collider Workshop '06 Resolution 'out of the box' : BPM 3-5: ~ 700 nm in x, BPM 9-11: ~350 nm in x 200 nm 20k pulses ~ 30 min Drift : need to understand !! old cavities prototypes

15. Phase systematics Vancouver Linear Collider Workshop '06 Resolution data from April run showed strong Q phase dependence Problem traced back to non-perfect filtering of 2ω peak + between sampling and downmixed separation between sampling and downmixed frequencies (reflection from upper nyquist band) Hardware solution : encrease LO by 10 MHz

16. Phase systematics, new LO frequency Vancouver Linear Collider Workshop '06 Effect on resolution : Better separated !

17. Interferometer Vancouver Linear Collider Workshop '06 M. Hildreth, M. Albrecht (Notre Dame) commissioned during July run commissioned during July run sub nm resolution sub nm resolution stability of < 30 nm (1 hr) with fixed mirror stability of < 30 nm (1 hr) with fixed mirror plan to link BPM stations plan to link BPM stations

18. Interferometer Vancouver Linear Collider Workshop '06 M. Hildreth, M. Albrecht (Notre Dame) commissioned during July run commissioned during July run sub nm resolution sub nm resolution stability of < 30 nm (1 hr) with fixed mirror stability of < 30 nm (1 hr) with fixed mirror plan to link BPM stations plan to link BPM stations

19. Future plans : running, calibration Vancouver Linear Collider Workshop '06 Analysis Analysis TODO: 24 hours stability data from July run Incorporate interferometer data Fully automatic calibration procedure for future chicane operation : tested during July run, in depth analysis needed

20. Future plans : hardware installation Vancouver Linear Collider Workshop '06 Hardware installation in the end station Hardware installation in the end station Upcoming run, early February 2007 Refurbish SPEAR magnets, map out and install Link BPM stations with interferometer (M. Hildreth) Install new prototype BPM (A. Liapine, UCL)  30 mm aperture, 2.878 GHz with 1.3 MHz bandwidth  theoretical resolution ~ 11.2 nm (assuming low electronic noise)  Design optimised for high resolution with lower frequency + temperature stability

21. Summary Vancouver Linear Collider Workshop '06 Intended setup and goals of T-474 experiment, with current installation Intended setup and goals of T-474 experiment, with current installation 2 runs so far with a small commissioning run in January 2 runs so far with a small commissioning run in January Installed interferometer Installed interferometer Resolution and stability goals achieved over short time scale (~30 min) Resolution and stability goals achieved over short time scale (~30 min) Analysis ongoing: long term stability, systematic effects, connecting different BPM stations Analysis ongoing: long term stability, systematic effects, connecting different BPM stations Future plans... Future plans... Thanks for your attention...