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The AD Schottky system (& future evolutions)

The AD Schottky system (& future evolutions). Maria Elena Angoletta CERN, AB/RF. CARE-N3-HHH-ABI Workshop Chamonix, December 11-13, 2007. Topics. CERN’s A ntiproton D ecelerator (AD): overview System overview: capabilities & layout Detectors: Schottky LPU + TPU

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The AD Schottky system (& future evolutions)

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  1. The AD Schottky system(& future evolutions) Maria Elena Angoletta CERN, AB/RF CARE-N3-HHH-ABI Workshop Chamonix, December 11-13, 2007

  2. Topics • CERN’s Antiproton Decelerator (AD): overview • System overview: capabilities & layout • Detectors: Schottky LPU + TPU • Processing: h/w + measurements • Results • Future work: ELENA ring • Conclusions Bonus slides M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 3/19

  3. CERN’s Antiproton Decelerator (AD) overview Some AD parameters. The momentum p during the AD basic cycle (2002 version). Needs How • New Schottky PUs (2x longitudinal + 2x transverse) Intensity Δp/p & <p> qH,V + εH,V Real-time during cycle + bunched/debunched beam • New digital processing system (DSP + DDC chips) . AD: pbars collection, cooling & deceleration. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 4/19

  4. System overview: capabilities LONGITUDINAL SIGNALS Bunched: intensity + bunch length by RF harmonics Fourier analysis (dual tracking DDCs). Debunched: intensity, p/p, <p> from Schottky signals (FFT-based spectral analysis). The only way to measure intensity essential! TRANSVERSAL SIGNALS FFT: qH,V + εH,Vfrom FFT-based sidebands spectral analysis. Implemented but not operational (low S/N ratio). BTF: qH,Vfrom Beam Transfer Function analysis. Bunched/ Debunched The only way to measure tune on ramps essential for short machine cycle. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 5/19

  5. System overview: layout TPU H/V Damper H/V selection LPU HF/LF Damper Stochastic/electron cooling Cooling status Summing Unit M-shaped noise gen. ADC DRX (DSP + 8xDDC) PPC VME bus Control/application layers Long. data BTF Control actions fREV AD ring hall Control room Clock gen. VME crate NIM crate M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 6/19

  6. Detectors: LPU[1] Two doubly-shielded ferrite cavities + ultra low-noise head amplifiers + equalised summing unit. Adjacent LF & HF LPUs - characteristics Beam transformer & amplifier – HF version. Low-noise feedback principles • High-Q resonant ferrite-loaded cavity reduces thermal noise current. • Broadband properties regained by low-noise high-impedance amplifier (JFET) + strong active feedback. [1] F. Pedersen at al., “An Ultra Low-noise AC Beam Transformer For Deceleration And Diagnostics Of Low Intensity Beams’, PAC ’99. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 7/19

  7. Detectors: LPU (cont’d) Low Transfer Impedance (LTI) cable • Medium wave radio noise on ~100 m ring-to-control-room cable. • Reason: CERN standard coax cable (C50-6-1) Zt ~5 mΩ/m @1 MHz. New industry (DRAKA)-developed cable (C50-6-2), Zt ~0.06 mΩ/m @1 MHz. Cable types: transfer impedance comparison LPU applications: • RF phase loop • Diagnostic (RF currents + Schottky scans) • LF LPU (TFA7049) in transfer line (single pass bunch intensity meas). NB: It works on pbars & protons!! M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 8/19

  8. Detectors: TPU[2] Problems • S/N worse than expected (6 dB). • No sharp minimum in common mode signal vs. beam position. Only BTF feasible (not Schottky analysis) Two electrostatic PUs (H + V) + ultra low-noise head amplifiers. Horizontal & vertical TPUs - characteristics • PUs resonant @5.6 MHz (Q = 900). • Low-noise feedback (same as LPU) to regain broad-band properties. TPU – construction overview. [2] O. Marqversen at al., “’Real-time Tune Measurements On The CERN Antiproton Decelerator’, DIPAC 2001. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 9/19

  9. Processing[3]: h/w DRX: Pentek 6510 • DDC: 8 x Harris HSP50016. • narrowband receivers (decimation 32 to 131072) • spurious free dynamic range > 102 dB. • DSP: TI ‘C40. Processing + DDCs setup. • Problemwith VME-global bus access arbitration. COTS ADC + DRX VME boards ADC: Pentek 6441 • AD9042: 12-bits, up to 41 MSPS. • Clock: • 40 MHz (flattops) • k∙fREV or (n±q)∙fREV ( ramps). • Problem: S/N ratio 15 dB worse than specs (!@*&) Pentek 6510 DRX board [3] M. E. Angoletta at al., ’ The New Digital-receiver-based System For Antiproton Beam Diagnostics ‘, PAC ‘01. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 10/19

  10. Processing: longitudinal debunched meas. • Noise offset calibration essential • S/N improved by FFT averaging. • Typical meas. rep. period: ~ 1.5 s. • Observation BW changed in FT (cooling). Ex: FT2 BW : 7 kHz → 3.5 kHz • intensity N • p/p, • <p> • averaged spectra Outputs • Intrinsically noisy: noise statistical properties (incoherent signal) observed. • Sensitive to instabilities, filamentation/ external noise…→Schottky power “explodes”. Longitudinal Schottky integrated power. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 11/19

  11. Processing: longitudinal bunched meas. • intensity (I0) • bunch length = f() Outputs Bunch approximation • Gaussian replaces initial parabolic approx. • Best suited for short bunches (beginning ramp). • ClockADC = k∙fREV , k integer, changed during ramp to have clockADC near 40 MHz. • Meas. rep. period = 20 ms • Coherent signals → high S/N Longitudinal bunched processing: RF harmonics Fourier analysis. Initial parabolic bunch approx. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 12/19

  12. Processing: intensity calibration 1 2 3 Bunched pbar intensity @ extraction vs. LF LPU in transfer line (TF7049). • TF7049 calibrated in absolute way via C discharge. • Assumptions: • flatness vs. frequency of LPU, amplifiers etc. • 100% extraction efficiency. Bunched pbar intensity vs. debunched Schottky meas. • Debunched intensity = f(GAIN2), bunched = f(GAIN). Bunched pbar intensity vs. DC beam transformer with protons • DC beam transformer calibrated + precise for high intensity. • Assumption: precision of transimpedance pbars/protons. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 13/19

  13. Processing: transverse BTF meas.[4] • Transfer function spectra (magnitude + phase). • Coherence function. • Beam & noise PSD spectra. Outputs BTF principle. M-shaped noise & setup params. • Semi-automated tune meas: user manually selects tune-bin in spectrum, application calculates tune. • M-shaped noise generation under user-control. [3] M. E. Angoletta at al., ’ Upgrades To The Digital-receiver-based Low-intensity Beam Diagnostics For CERN AD ‘, PAC ‘03. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 14/19

  14. Results – intensity Instabilities and/or poor statistics. fREV NP Low S/N p/p RF ON Incomplete debunching. Ejection Bunched-debunched transitions. Intensity, revolution frequency and p/p in AD cycle (screenshot taken in 2002 ). M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 15/19

  15. Results – BTF Meas setup params Calculated tune DDC cutoff filter BTF on bunched beam @ ramp 2 (screenshottaken in 2004). M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 16/19

  16. Future work: proposed ELENA[5] ring Extra Low ENergy Antiprotons (ELENA): compact ring for post-ADpbars deceleration & cooling. Some ELENA parameters. LPU • [20 kHz – 25 MHz] range. Same design (shorter?) as AD LPU. • Use: phase loop, bunch length, intensity from RF currents, Schottky scans. Processing • Diagnostics integrated in RF system • Hw: DSP/FPGA motherboard + daughtercards (MDDS, SDDS, DDC) deployed in Low Energy Ion Ring (LEIR) LLRF[6] : • Reduced cost/channel. • Digital BTF noise generation. Same advantages: [5] T. Eriksson [ed.], “’ ELENA: A Preliminary Cost And Feasibility Study’”, CERN-AB-2007-079. [6] M. E. Angoletta et al., “First Experience With The New LEIR Digital Beam Control System”, AB-Note-2006-003-RF. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 17/19

  17. Future work: proposed ELENA ring (cont’d) M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 18/19

  18. Conclusions • Schottky signals: rich in information & excellent diagnostics means with no beam perturbation. • BTF: may not disturb the beam if optimised noise. • AD system: based on low-noise detectors (LPU, TPU) + digital processing. • Most essential AD diagnostics! • Future developments: ELENA. Same processing as AD’s but on custom hardware deployed in LEIR. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 19/19

  19. AD ring Protons via the loop, not used anymore. Target Area: 26 GeV/c protons 3.57 GeV/c pbars Experimental Area AD ring and hall. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 20/19

  20. Additional slides on AD Schottky system M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 21/19

  21. Double-Shielded Copper Cavity M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 22/19

  22. LPU HF: noise levels M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 23/19

  23. LPU LF :noise levels M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 24/19

  24. LTI cable: construction M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 25/19

  25. LTI cable: construction (cont’d) CERN C50-6-2 LTI cable construction. M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 26/19

  26. LTI cable: electrical properties M. E. Angoletta “The AD Schottky system” CARE-N3-HHH-ABI Workshop, Chamonix, 2007 27/19

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