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EMMA Diagnostic devices FNAL

EMMA Diagnostic devices FNAL. Jim Crisp December 2007 (updated for 3-10psec sigma bunch length). overview. 3 WCM’s (Wall Current Monitors) beam charge bunch phase or timing bunch shape (limited 4GHz bw = 40ps sigma t) 89 BPM receivers (Beam Position Monitors)

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EMMA Diagnostic devices FNAL

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  1. EMMA Diagnostic devices FNAL Jim Crisp December 2007 (updated for 3-10psec sigma bunch length)

  2. overview • 3 WCM’s (Wall Current Monitors) • beam charge • bunch phase or timing • bunch shape (limited 4GHz bw = 40ps sigma t) • 89 BPM receivers (Beam Position Monitors) • 4 injection, 82 ring, 3 diagnostic • YAG:Ce screens (profile monitor screen) • Yttrium Aluminum Garnet activated by Cerium • Convey few words

  3. WCM details • Basically one turn transformer • ceramic vacuum break and magnetic core • 40mm aperture, 110mm length • Microwave cutoff in beam tube defines upper frequency limit • 4.4GHz for 40mm ID round pipe • difficult to separate signals propagating along beam pipe from those induced by beam charge • microwave chip resistors and flexible circuit board used to form resistive combiner are good for ~10GHz • Tested with 50ohm structure with higher cutoff frequency • 4 equally spaced pickoff points provide a measurement reasonably independent of beam position and rejects non TEM modes by symmetry

  4. WCM ferrite • 2ohm gap would provide reasonable signal • Terminates modes in ceramic • 0.32Vp for 32pC (40psec response) • desire droop time constant much longer than 830nsec • (15 turns X 55.3nsec/turn) • Ceramic Magnetics MN100 ferrite core • 24uH = N^2 uA/L (for N=1turn) • 2ohm 24uH = 12uSec (13.4KHz) • 1024 turns (55usec) will show significant droop • Could restore background in software • 15KHz to 4GHz bandwidth

  5. WCM bandwidth • 4.4GHz microwave cutoff for 40mm ID • 13KHz to 4GHz WCM bandwidth • 4GHz ==> 40psec risetime • Can’t resolve bunch structure • 3psec (0.9mm) sigma bunch length • 53GHz sigma frequency content • 80pC in 3psec would have 11Amps peak • Will microwave power launched by beam passing discontinuities in the beam pipe cause problems? • arcing or interference with diagnostics?

  6. Fermi Linac WCM

  7. Frequency Response • Measured with 50ohm test fixture to overcome microwave modes in pipe • ‘wiggles’ are from small mismatch in test fixture • (2ohms/50ohms = -26db)

  8. Tektronix ‘DPO71254’ Windows based operating system 4 channels 50Gs/s 10Meg 200usec of memory 12.5GHz bandwidth 23psec risetime 10mV to 1V/div 10ps to 1000s/div $88500 4 week lead time Agilent ‘DSO81204’ Windows based operating system 4 channels 40Gs/s 4Meg (opt 001) 100usec of memory 12.0GHz bandwidth 26psec risetime 1mV to 1V/div 10ps to 1000s/div $92538 (+$5184 opt 001) 5 week lead time possible oscilloscopes

  9. WCM notes • Develop algorithms in LabView • Could be moved to EPICS • Bandwidth limited to <4.4GHz by microwave cutoff • 50Gsps scope = 20psec/sample • need to limit bandwidth of signal • 4th channel on scope could digitize rf fanback signal • wideband buffer amp to share WCM signal • short low dispersion cables require good termination • Required charge and phase accuracy • 1% charge, 2 deg at 1.3GHz (4.3psec) • Waiting for approval to spend money

  10. BPM details • 4 injection, 82 ring, 3 diagnostics • position, charge, time of flight • measure single bunch each turn for 15 turns (55.3nsec/turn) • 1000 turns for commissioning? • bunch charge 16pC min / 32pC max • 50um / 25um resolution • bunch length 3 to 10psec sigma • longer bunches? (may affect design) • 48mm ID with four 20mm buttons • 3.7GHz microwave cutoff for 48mm round pipe • Pos = 12.65(A-B)/(A+B) • 25um desired alignment error • Evaluate with ERLP beam (summer 2008) • Install Feb – May 2009 • Beam July 2009

  11. BPM approach • Digitizing 3 to 10psec bunch directly is not practical • Diode detector requires matched diodes and careful temperature compensation • Switches require accurate, stable timing • Downconverters need to be carefully matched and stable (used on atf at KEK) • (~10um single bunch single turn resolution with 50e8) • Started looking at their design • Consider RLC to produce a decaying sinewave from bunch transient • Use 500MHz 12bit adc

  12. estimate frequency content • Bunch length and button shape determine frequency content of the bpm signals • bpm peak when button is ¼ wavelength in diameter, zero when ½ wavelength • 3.75GHz peak, 7.5GHz zero • 3psec sigma t (gaussian) bunch corresponds to 53GHz sigma f (gaussian) • (10psec / 16GHz) • Beam pipe is a complex shape but microwave cutoff in 48mm round pipe is 3.7GHz

  13. estimate button current • difference of two gaussian 20pC 10psec sigma bunches displaced in time by 20mm/c = 133psec • 2.5pC in each half of the doublet • Independent of bunch length for bunch << button length

  14. 400MHz 100ohms • 100ohms, 12nsec, 60pf, 2.64nH, Q=15 • 20pC, 10psec, 20mm button • 2.5pC in 60pf = 41.7mV • 6.65mVpk of 400MHz • Independent of bunch length for bunch << button length • Rms value averaged over 55ns • 0.233*6.65mVpk = 1.55mVrms

  15. ringing filter • signal must decay to 1% in 55nsec (1 turn) • Insures signal from 1 turn does not corrupt the next • 12nsec 1/e time constant • A 400MHz signal sampled at 500MHz looks like 100MHz

  16. signal processing • For each turn (27 samples) • Multiply samples by sin(t) and integrate (As,Bs) • Multiply samples by cos(t) and integrate (Ac,Bc) • Could use decaying sinwaves but advantage is small • t = {atan(As/Ac) + atan(Bs/Bc)}/ 2 • Intensity = A+B • (A = sqrt(As^2+Ac^2) for plate A) • Position = 12.65mm(A-B)/(A+B)

  17. expected errors • for a full scale peak signal (2.2Vp-p) (gain of 110 for 32pC) • rms of decaying sinewave, 27 samples, R = 12.65mm (cal or gain) • 2.2Vp-p* ½ *0.233 = 0.26Vrms • SINAD (signal to noise and distortion) • 4.3um • 0.14psec • INL (integral nonlinearity error) • 2.0um • 0.07psec • AU (aperture uncertainty) • 3.4um (proportional to frequency) • 0.11psec • thermal noise for 100ohm 400MHz RLC (25MHz bandwidth) • Cannot be improved with an amplifier • 2.5um • 0.08psec • Totals (larger with smaller signals and larger positions) • Allowing for 20mm position requires 15db or 5.62 headroom • 36um • 1.1psec

  18. Fermi digitizer board • Currently designing ATCA board for ILC test linac • ATCA – ‘Advanced Telecommunications Computing Architecture’ • FPGA with enough memory to sample all 15 turns at 500MHz • Field Programmable Gate Array • 16 dac channels AD97736 • 12 bit 1200msps • 16 adc channels ADS5463 • 12 bit 500msps • SINAD 64.3dbc (signal to noise plus distortion) • AU 0.16psec (aperture uncertainty) • INL 1lsb (integral nonlinearity error) • 2.2Vpp max input • Prototype board expected 3/2008 • Test with ERLP beam? • Final design 6/08 • EMMA Installation 2/09 • EMMA Beam 7/09

  19. ATCA Digitizer Development DDR2 SDRAM 1GB FLASH 256MB ATCA Digitizer Diagram ATCA Backplane ATCA Rear Transition Board 1GSPS Serial Link Full Mesh 4 +4 Channels ADC&DAC Module DDR2 Controller FPGA STRATIX II EP2S60F1020 Fabric & Base Ethernet Interface NIOS II Fabric Interface Full Mesh 4 +4 Channels ADC&DAC Module Analog Inputs Ch1 - ch16 Analog Outputs Ch1 - ch16 10/100/1,000 ETHERNET 4 +4 Channels ADC&DAC Module Base Interface 10/100/1,000MB Ethernet 10/100/1,000 ETHERNET 4 +4 Channels ADC&DAC Module Intelligent Platform Management Bus IPMB-A IPMB-B IPMC Clock Synthesizer and Distribution AD9510 Hot Swap Power Controller, Low Noise, Slew Control Spread Spectrum DCDC Digital IO: Ext Clock, Ext Trigger, Ext Gates, Front-End Control Ext CLK Int CLK 48V A Power 48V DC 200W 48V B 19

  20. bpm system • Each ATCA crate would have a front end or ‘slot zero controller’ that processes and delivers data to an EPICS data base via ethernet • Each ATCA crate would likely have one timing distribution card • The EPICS application is important and represents significant effort carefully coordinated with physics requirements of the machine. • Scott Berg, Shinji Machida have some excellent ideas

  21. conclusions • A simple resonant filter was explored. • peak signal independent of bunch length for bunch << button length • Need bpm to proceed • A down converter should be considered • Still use resonator on button • Looking at KEK atf design • The bpm signal amplitude should match the adc input range • need amplifier (gain of ~100), antialiasing filter before adc • Small interface board in ATCA crate • A/B will change by up to 10db (factor of 3) with position • bunch charge can change from 20 to 80pC (factor of 4) • Bunch length likely to change from 3 to 10psec sigma • 12um rms error for full scale inputs could increase to 144um rms • Make sure modeling program requirements are met

  22. for exampleRecycler digital receivers • Simulate receiver inputs to model constant position with changing intensity • 14 bit 80MHz adc’s, 120 samples, 63mm radius • each position measured 100 times • Mean is plotted on the left and the standard deviation is on the right

  23. Recycler adc linearity • Difference between previous slide measurements and horizontal lines • Position depends on linearity of A and B adc’s • Dotted lines from 0.3bits typical for the adc • Solid lines indicate error from previous slide

  24. YAG:Ce profile monitor screens • Harvested from the brain of Ardin Warner: • www.crytum.com • YAG:Ce - Yttrium aluminum garnet activated by cerium is a fast scintillator. The material's mechanical properties enable production of thin screens down to 0.005 mm thick. • They can drill holes or apply scribe lines for optical reference • Adjusting the doping can provide relaxation times that allow separation of turns (<50nsec) • 30mm diameter 100um thick $100

  25. YAG:Ce & Fermi eCool • Arden Warner and others use YAG:Ce 100um thick 30mm diameter screens to measure 4.36MeV electron beam of 500mA, 2usec (6.25e12) with 1Hz rep rate. • use gated CID camera 800x600 pixels $8k • gate can be 20nsec • 50um resolution • National Instruments 'Vision' for processing data • 'imageJ' is also very good and it’s freeware

  26. eCool beam Picture of YAG:Ce used in the electron cooler A couple of images taken with a gated CID camera. The gate width here is 100ns but the camera system can be gated as short as 200 ps which is not necessary in cooler application. The electron beam is a 2µs pulse at 1Hz rep rate, 100 -500 mA. YAG/Pepper- pot image of the beam before adjustments. Photo’s courtesy of Arden Warner, Fermilab

  27. Summary • Ready to start spending money on WCM’s • Need bpm to develop analogue front end • 4 feedthroughs would allow me to build prototype at Fermi • Bpm time line is tight • Fermi has deployed digital bpm systems in Recycler, Main Injector, Tevatron, and atf at KEK. • They are expensive but work well • A commitment would help leverage resources to insure time requirements are met • Perhaps a commitment to purchase 1 digitizer, ATCA crate, and controller? (~$24k US) • 384 heavy stiff bpm cables attached to expensive/fragile vacuum feedthroughs • Need to provide for interface bracket attached near bpm • Can they follow the girder? • Spares? • I don’t know anything about screens • Arden Warner, Alex Lumpkin do.

  28. resolution vs accuracy • 25um resolution • very surprised if physical bpm is linear to that accuracy even with mapping • hor/ver positions are coupled • 12.65mm(A-B)/(A+B) ~ 0.72mm/db • 25um = 0.035db • Cable aging, bending, cable temperature, humidity, changes in termination, integrity of connections, number of connection cycles, corrosion • Should incorporate some ‘calibration’ feature

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