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Novel Beam Instrumentation for Future Linear e + /e - Colliders

Novel Beam Instrumentation for Future Linear e + /e - Colliders. Anne Dabrowski Northwestern University Mayda Velasco (NU), Hans Braun (CERN) Thibaut Lefevre (CERN) Bag Lunch Seminar Northwestern University February 21 st 2007. A. Dabrowski, February 21 2007. 1/25.

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Novel Beam Instrumentation for Future Linear e + /e - Colliders

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  1. Novel Beam Instrumentation for Future Linear e+/e- Colliders Anne Dabrowski Northwestern University Mayda Velasco (NU), Hans Braun (CERN) Thibaut Lefevre (CERN) Bag Lunch Seminar Northwestern University February 21st 2007 A. Dabrowski, February 21 2007 1/25

  2. Motivation: TeV lepton collider Slide R Corsini S. Redaelli 2/25 A. Dabrowski, February 21 2007

  3. CLIC Slide, T Lefevre • High luminosity 3TeV Collider based on the ‘Two Beam Scheme’ • High accelerating field of 100MV/m

  4. CLIC RF power source – ‘Drive Beam’ ‘Colliding Beams’ • Efficient way of producing RF power with a Drive Beam: • Fully beam loading acceleration in the drive beam linac • Flexible and precise bunch frequency multiplication using RF deflector injection techniques in a delay loop and combiner rings • Efficient deceleration sections with a high Beam to RF conversion efficiency.

  5. CLIC parameters Most Critical Beam Parameters for diagnostics Machine is in design phase, parameters constantly being optimized for performance & cost. Above parameters are typical examples. 5/25 A. Dabrowski, February 21 2007

  6. Drive Beam Parameters Slide, reference T. Lefevre CERN Academic Training Lecture June 16 2006 Diagnostics on the beam is important in order to prevent damage of machine. 6/25 A. Dabrowski, February 21 2007

  7. Drive Beam Injector PETS Line 30 GHz source Delay Loop Drive Beam Accelerator TL1 (2006) Stretcher CR (2006) RF photo-injector test (2006-2007) 30 GHz tests CLEX (2007) TL2 (2007) Overview 3rd CLIC Test Facility Electron beam facility • 1.5microsecond pulse • 150MeV electron LINAC • 3.5 Amp current • Newly commissioned delay loop • Very rich environment for beam instrumentation development 7/25 A. Dabrowski, February 21 2007

  8. Northwestern CTF3 Activities Drive Beam Injector PETS Line 30 GHz source Delay Loop TL1 (2006) Drive Beam Accelerator Stretcher CR (2007) RF photo-injector test (2006-2007) 30 GHz tests CLEX (2008) TL2 (2007) Pickup for Bunch Length Measurement Beam Loss Monitoring 8/25 A. Dabrowski, February 21 2007

  9. Outline • RF pickup for bunch length measurement • Principle of the measurement • Report on activities during 2006 • Hardware designed, installed & tested • Electronics • Software • Results of data taking in the Fall • Future improvements to setup 9/25 A. Dabrowski, February 21 2007

  10. Theory Power Spectrum [a.u.] Freq [GHz] Principle of the measurement The RF-pickup detector measures the power spectrum of the electromagnetic field of the bunch For a given beam current; the larger the power spectrum amplitude, the shorter the bunch length. Picked-up using rectangular waveguide connected to the beam pipe, followed by a series of down-converting mixing stages and filters. Solid: σt = 1 ps Dash: σt = 2 ps Dash-dot: σt = 3 ps Power Spectrum [a.u.] Theory Freq [GHz] 10/25 A. Dabrowski, February 21 2007

  11. Advantages of the RF-Pickup • Advantages • Non-intercepting / Non destructive • Easy to implement in the beam line • Relatively low cost (compared to streak camera and RF deflector) • Relatively good time resolution (ns)  follow bunch length within the pulse duration • Measure a single bunch or a train of bunches • Relative calibration within measurements • Short comings in the calibration • Beam position sensitive • Sensitive to changes in beam current • At CTF3: the RF deflector and/or a streak camera can provide an excellent cross calibration of device 11/25 A. Dabrowski, February 21 2007

  12. RF-pickup device installed in CTF2 • An RF pickup was installed in CTF2 • Rectangular waveguide coupled to a rectangular hole made on the beam pipe surface • Using the mixing technique it measured bunches as short as 0.7ps. It was limited by a maximum mixing frequency of 90 GHz. • This device was dismantled in 2002  was no longer being used at CTF3. • Goal is to re-install the device with an improved design • Increase maximum frequency reach max mixing of 170 GHz, to reach bunch length measurements of 0.3ps. Invested + commissioned D-band waveguide components & mixer @ 157 GHz • Design a ceramic/diamond RF window for good vacuum and transmission at high frequency • Spectral analysis by single shot FFT analysis from a large bandwidth waveform digitizer C. Martinez et al,CLIC note 2000-020 12/25 A. Dabrowski, September 05 2006

  13. Investment in new hardware • Local oscillator (Down converter) • LO 157 GHz • RF 142-177 GHz • D-band waveguide components (waveguide WR-6 1.65 mm x 0.83 mm, cutoff 110 GHz) • D-band Horn (gain 20dB) • D-band fixed attenuator (10 dB) • D-band waveguide 5cm • Brass high pass filter, size of holes determine cutoff 13/25 A. Dabrowski, February 21 2007

  14. 4 2 1 3 New Detector Setup CT-line, BPR and single WR-28 waveguide to transport the signal to the gallery (~20 m). Analysis station gallery • Filters, and waveguide pieces separate the signal from the beam into 4 frequency-band detection stages: • (30 – 39) ; (45-69) ; (78-90) & (157-171) GHz • Series of 2 down mixing stages at each detection station. From the beam 14/25 A. Dabrowski, February 21 2007

  15. Electronics for Acquisition Acqiris DC282 Compact PCI Digitizer 4 channels 2 GHz bandwidth with 50 Ω standard front end 2-8 GS/s sampling rate Signals from Acqiris scope visible in control room for real time monitoring & DAQ 15/25 A. Dabrowski, February 21 2007

  16. DAQ and Analysis code Software: Data acquisition controlled by a Labview program, with built in matlab FFT analysis routine. Code to extract the bunch length in real time written. System used from control room in regular running operation Labview interface Raw Signal FFT Signal Screen for analysis 16/25 A. Dabrowski, February 21 2007

  17. Bunch length manipulation in the INFN chicane Slide T. Lefevre Accelerating structures @Girder 15 4 Bends Frascati Chicane Delay Loop RF pick-up Lower energy Nominal energy Higher energy Changing the phase of Klystron 15 to insert a time to energy correlation within the bunch Convert energy correlation into path length modification and time correlation Measure the Bunch frequency spectrum Klystron V(t) • On-crest Acceleration – the bunch length is conserved through the chicane • Positive Off-crest Acceleration – the bunch gets shorter • Negative Off-crest Acceleration – the bunch gets longer t 17/25 A. Dabrowski, February 21 2007

  18. Calibration of device – RF Deflector Screen RF Deflector Magnetic chicane (4 dipoles) sy0 Deflecting Voltage RF deflector phase RF deflector off RF deflector on sy Betatron phase advance (cavity-profile monitor) Bunch length RF deflector wavelength Beam energy Beta function at cavity and profile monitor Deflecting mode TM11 Chicane optics & bunch length measurements - 2004 Slide T. Lefevre 18/25 A. Dabrowski, February 21 2007

  19. Calibration of device – RF Deflector sy0 sy Deflecting mode TM11 SR@ MTV0361 OTR@ MTV0550 Calibration Strategy: For various settings on the chicane, take bunch length measurements using both the RF deflector, and the RF-pickup. Calibrate the response function of the pickup. Once calibrated, the pickup can be installed anywhere else in the machine where a bunch length measurement is needed. The RF-pickup is a much less expensive device than the RF deflector & Streak camera. RF-pickup better resolution than the Streak camera ( < 2ps). s = 8.9ps s = 4.5ps 19/25 A. Dabrowski, February 21 2007

  20. Typical Raw and FFT pickup signals Example: Synthesizer (second down-mixing stage) set at 5300 MHz phase MKS15 355 degrees, 06-12-2006 Raw signals from the beam in time domain Fourier Transformed signals 63 GHz, 51 GHz 33 GHz FFT 81 GHz 162 GHz 10 measurements, at each local oscillator & phase setting. FFT done on each measurement  result averaged, std dev of mean < %. 20/25 A. Dabrowski, February 21 2007

  21. Theory Power Spectrum [a.u.] Freq [GHz] Reminder of the Theory (30 – 39) ; (45-69) ; (78-90) & (157-171) GHz • Measure the power spectrum at each frequency band: • The maximum height of each FFT peak. • Fit to the best bunch length, σt 21/25 A. Dabrowski, February 21 2007

  22. Bunch length measurement result preliminary • Data analysed using a self calibration procedure, by means of Chi square minimization. • 16 measurements (corresponding to the 16 phases on MKS15) • Fit done with lowest 3 mixing stages. • 19 free parameters fit  3 response amplitudes and 16 bunch lengths • Sub-pico second sensitivity reached. • Self calibration method used & reliable (many measurements taken & consistent) •  next step to improve & optimize setup 22/25 A. Dabrowski, February 21 2007

  23. Improvement: Increase transmission @ high frequencies  New RF Window in design @ 90 GHz through Al203λ is effectively ~ 1 mm Although obtain Good signal in December commissioning of RF-pickup ; Al203 window not optimized for good transmission at high frequencies (> 100 GHz)  designed a thin (0.5mm) diamond window with lower εr. First design complete, brazing test successful, machining in progress  testing to follow Will test new window in 2007 23/25 A. Dabrowski, February 21 2007

  24. 4 2 1 3 Improvement in setup foreseen Analysis station gallery • Note: • At high frequency mixing stage: • High Pass filter @ 157 GHz; (157 + 14) GHz signal is analysed in 4th mixing stage. • Modifying the high pass filter to 143 GHz would allow (157 ± 14) GHz to be simultaneously analysed  sample more frequencies • Modify filters to have spherical shape, to focus signal,  capture more power  higher signal. From the beam 24/25 A. Dabrowski, February 21 2007

  25. Summary: Bunch Length detector • RF-pickup detector has been successfully installed in the CT line in CTF3 • Bunch length measurement made as a function of phase on MKS15! • The Mixer & filter at 157 GHz was tested and works. • Using Single waveguide to Pickup signal works. • The new acquires data digitizing scope installed, online analysis and DAQ code tested and working. • Self calibration procedure stable. Possible improvements to the setup: • Improved RF diamond window for high frequenciesis being machined and brazed and will be installed for future tests. • An additional filter at ~143 GHz, can provide additional flexibility in the detection of high frequency mixing stage. • Spherical surfaces on the filters to better focus the signal on the analysis board, through the detector stages. 25/25 A. Dabrowski, February 21 2007

  26. s 1 n! Why is this measurement needed? Performances of Bunch Length detectors (T. Lefevre, CERN) Limitations • Optical radiation • Streak camera -------------------- xxxxxxx xxxxxxx > 200fs • Non linear mixing ----------------- xxxxxxx xxxxxxx Laser to RF jitter : 500fs • Shot noise frequency spectrum -- xxxxxxxxxxxxxx Single bunch detector • Coherent radiation • Interferometry ------------------- xxxxxxxxxxxxxx • Polychromator --------------------- xxxxxxxxxxxxxx • RF Pick-Up -------------------------------- xxxxxxxxxxxxxxxxxxxxx> 500fs • RF Deflector ----------------------------- xxxxxxxxxxxxxxxxxxxxx • RF accelerating phase scan -------------- xxxxxxx xxxxxxxxxxxxxx High charge beam • Electro Optic Method • Short laser pulse ------------------ xxxxxxxxxxxxxxxxxxxxx Laser to RF jitter : 500fs • Chirped pulse ----------------------xxxxxxxxxxxxxxxxxxxxx > 70fs • Laser Wire Scanner ---------------------- xxxxxxxxxxxxxxxxxxxxx Laser to RF jitter : 500fs A. Dabrowski, February 21 2007

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