1. ATLAS Forward Proton Electronics Andrew Brandt, University of Texas at Arlington 1 AFP concept: adds new ATLAS sub-detectors at 220 and 420 m upstream and downstream of central detector to precisely measure the scattered protons to complement ATLAS discovery program. These detectors are designed to run at a luminosity of 10 34 cm -2 s -1 and operate with standard optics (need high luminosity for discovery physics) beam p’ AFP Detector LHC magnets 420 m 220 m H After 1+ year of ATLAS internal review, AFP recently approved to proceed to Technical Proposal

2. What is AFP? 1)Impressive array of rad-hard edgeless 3D silicon with resolution ~10  m, 1  rad 2) New Connection Cryostat at 420m 3) “Hamburg Beam Pipe” instead of Roman Pots 4) Timing detectors with ~10 ps resolution for overlap background rejection 2January 28, 2010Andrew Brandt Clermont-Ferrand Use time difference between protons to measure z-vertex and compare with tracking z-vertex measured with silicon detector (x20 rejection with 10 ps timing resolution) Ex: Two b-jets from one interaction and two protons from another

3. Allows ATLAS to use LHC as a tunable  s glu-glu or  collider while simultaneously pursuing standard ATLAS physics program What does AFP Provide? 420- 420 420- 220 220- 220 3 Mass and rapidity of centrally system where  1,2 are the fractional momentum loss of the protons Mass resolution of 3-5 GeV per event Acceptance >40% for wide range of resonance mass Combination of 220 and 420 is key to physics reach!

4. Timing System Requirements 10 ps or better resolution Robust: capable of operating with little or no intervention in radiation environment (tunnel) ~100% efficiency Acceptance over full range of proton x+y Segmented (multi-proton timing) High rate capability Two main options: 1) one very precise measurement (GASTOF) 2) multiple less precise measurements (QUARTIC) Andrew Brandt Clermont-Ferrand4January 28, 2010

5. 4x8 array of 5-6 mm 2 fused silica bars QUARTIC UTA, Alberta, Stonybrook, FNAL Multiple measurements with “modest” resolution simplifies requirements in all phases of system 1) We have a readout solution for this option (subject of this talk) 2)We can have a several meter cable run to a lower radiation area where electronics will be located 3) Segmentation is natural for this type of detector proton photons Only need a 40 ps measurement if you can do it 16 times: 2 detectors with 8 bars each, with about 10 pe’s per bar 5

6. MCP-PMT Requirements Excellent time resolution: 20 ps or better for 10 pe’s High rate capability: I max = 3  A/cm 2 Long Lifetime: Q= 30 C/cm 2 /year at 400 nm Multi anode: pixel size of ~6 mm x 6mm Tube Size: 40 mm round, 1 or 2 inch square Pore Size: In our experience 10  m or better We need 4/5 of tough requirements (only thing we don’t need is large area!) 6

7. Components of AFP Fast Timing System QUARTIC: Photonis planacon (10  m pore 8x8) or 40 mm Photek MCP-PMT Mini-circuits ZX60 3 GHZ or equivalent Louvain Custom CFD (LCFD) HPTDC board (Alberta) Reference Timing Opto- modules/ ROD HV/LV UTA QUARTIC/PMT Development Stonybrook AMP to HPTDC Manchester/UCL Ref. time SLAC +LLNL <1 ps !

8. January 28, 2010Andrew Brandt Clermont-Ferrand8 Fourier Transform of Signal -whole signal is in first GHz -scope bandwidth is 6 GHz -cell phone/wireless noise contributions visible -we use high bandwidth amp because of low noise and then add filtering. A 1 GHz low noise amplifier would likely be preferable, but we couldn’t find one so we filter (1.5 GHz filter helps a little, 1 GHz starts to cut into signal degrade performance) 10  m planacon, 40 pe’s Lecroy 8620A Wavemaster 6 GHz 20 Gs/s 1 GHz

9. LCFD LCFD (Louvain Constant Fraction Discriminator) 12 channel NIM unit mini-module approach tuned to PMT rise time Excellent performance : <10 ps resolution for 4 or more pe’s Remote control for threshold ZX60 3 GHz amplifier (we use pairs of 3,4, 8 GHz amps in different combinations to control total amplification) 9January 28, 2010Andrew Brandt Clermont-Ferrand

10. 10 LCFD Performance 100 pe’s V Use large light signal to get narrow pulse width and attenuators to evaluate LCFD “sweet spot” LCFD prefers >200 mV Note our scope resolution is about 2 ps (measured using splitter after LCFD)

11. January 28, 2010Andrew Brandt Clermont-Ferrand11 LCFD Resolution Pulses are amplified such that the mean pulse height is 500 mV (Note: must optimize every measurement this way—any time you vary the pulse height by changing HV or number of PE’s must check that you are still in the sweet spot of LCFD)

12. January 28, 2010Andrew Brandt Clermont-Ferrand12 LCFD Performance Using attenuators can measure the time shift as a function of pulse height for a fixed number of pe’s, and determine a residual correction factor as a function of pulse height, which we can apply for any number of pe’s: but LCFD is so good this is not really necessary Vps

13. January 28, 2010Andrew Brandt Clermont-Ferrand13 Alberta HPTDC Board Targeting ~20 ps RMS resolution; (STAR TOF reported 24 ps, ALICE TOF reported 20 ps, Ref: 1,2) 8 differential LVPECL input channels ; 1 HPTDC (v1.3) chip from CERN in Very High Resolution Mode; Altera Cyclone2 FPGA, Cypress USB chip for local debug; Serial LVDS link to connect to the main RODs (ATLAS Readout) Both USB and the Serial LVDS link provide timing and control signals to HPTDC Ref 1: J. Schambach, “Proposed STAR time of flight readout electronics and DAQ”, Computing in High Energy and Nuclear Physics, 24-28, March 2003, La Jolla, California. Ref 2: P. Antonioli, “A 20 ps TDC readout module for the ALICE time of flight system: design and test results”. 9th Workshop on Electronics for LHC Experiments, Amsterdam, The Netherlands, 29 Sep - 3 Oct 2003, pp.311-3159th Workshop on Electronics for LHC Experiments Jim Pinfold Shengli Liu

14. Alberta HPTDC board 12 ps resolution with pulser including non- linearity corrections. Successfully tested at UTA laser test stand with laser/10  m tube/ZX60 amp/LCFD 14January 28, 2010 13.7 ps with split LCFD signal Andrew Brandt Clermont-Ferrand

15. Concern: During discussions at Photek we learned that occupancy of HPTDC would be a problem for >2 MHz (this is in the manual, but who reads manuals?) Study used HPTDC Verilog model & measurement, simulation details: At high luminosity, the hottest pixel would see a rate of 10-15 MHz The minimum spacing between triggers is 25 ns ATLAS L1 trigger rate 100 KHz, with a trigger latency of 2.5  s; QUARTIC HPTDC Buffering January 28, 201015Andrew Brandt Clermont-Ferrand

16. QUARTIC HPTDC Buffering January 28, 201016Andrew Brandt Clermont-Ferrand

17. Only input channel 0 is connected (4 useful channels/ chip instead of 8) Hit rate (MHz)Total hitsLoss hitsLoss rate 4719079.74e-4 65117458.79e-3 831601073.39e-2 1014241188.29e-2 127391110.15 14306600.196 \ Hit rate (MHz)Total hitsLoss hitsLoss rate 85324411.88e-5 10778322.57e-4 12907266.61e-4 1510713121.12e-3 185998335.5e-3 202404271.12e-2 222589371.43e-2 242747792.88e-2 BufferingResults – Loss Rate BufferingResults – Loss Rate Loss rate in channel buffer for Logic core clock = 40MHz Loss rate in channel buffer for Logic core clock = 80MHz January 28, 201017Andrew Brandt Clermont-Ferrand

18. Standard version of HPTDC chip works with a core clock frequency up to 80 MHz A special speed graded version of HPTDC chip could work with core clock of 160 MHz. RMS resolution is not affected when running with 80MHz clock. Occupancy at trigger and readout FIFO’s is low enough Modest increase in power consumption Buffering Test Results January 28, 201018Andrew Brandt Clermont-Ferrand

19. January 28, 2010Andrew Brandt Clermont-Ferrand19 Reference Timing Reference timing is needed to connect two arms ~1km apart; what we want is T L - T R, what we measure is (T L -T ref )-(T R -T ref ), so need small jitter in T ref This setup has been tested to give 150 fs with 100m cable (1km cable isexpensive!) The reference system uses a phase lock loop to maintain a constant number of wavelengths in a 100m cable. This synchronizes the phase of the RF at each end of the cable. A voltage controlled oscillator (VCO) launches a signal down the cable where it is reflected and sent back. The returned signal is then interfered with an external RF reference to synchronize it with the reference. At the end of the 100m cable the signal is sampled with a directional coupler which mixes the signal to produce a DC level. That DC level is fed back to the VCO to maintain a constant number of wavelengths in the cable.

20. Ref. Timing Rate Reduction Concern: integrating reference time into DAQ Planned to dedicate one channel/chip to reference time signal However reference time needs to be available every 25 ns: 40 MHz (too high!) Actually we only need reference time for good events! 1) Form a trigger based on multiplicity of CFD signals in one row -example if at least 4/8 bars have a signal 2) Only send CFD signals to HPTDC board if trigger is satisfied 3) Trigger reference time signal as well, so a chip will have 4 inputs: three bars in the row where trigger was satisfied, and the ref time signal corresponding to that row 4) Also keep some prescaled signals for monitoring Select the reference timing edges and CFD signals to HPTDC board by following conditions: CFD signals arrive within 2 ns window of “Enable” ( 2ns corresponds to full vertex coverage at ATLAS +/- 30 cm (expect all events in a 2 ns window) A predefined multiplicity coincidence “trigger” be met for above CFD signals; The reference edges related to above CFD signals are passed. January 28, 201020Andrew Brandt Clermont-Ferrand

21. L1 TRIGGER The Trigger formed in previous slide for controlling reference time rates can also be used for a L1 Trigger! The total number of trigger bits we send back to ATLAS for L1 is a balance between: Optimal binning to give the lowest background trigger rate (when combined with jet information from calorimeter) The practical limits on the number of cable connections we can make, serial transmission schemes, and CTP input availability. The simplest scheme involves sending four bits directly over individual cables (low, intermediate, high, very high mass, for example). Large diameter air core cables are required to minimize the cable delay due to latency concerns. 21

22. January 28, 2010Andrew Brandt Clermont-Ferrand22 We have developed a fast timing system for AFP that seems to be capable of ~10 ps resolution Test beam is planned for this year with an 8-channel prototype system from the detector through to ATLAS readout. Work in progress: 1) final optimization of detector (looking into quartz fibers—could lower maximum rate by 2-3 by more sensible binning) 2) developing and testing long-life MCP-PMT 3) evaluating radiation tolerance of all components and upgrading as needed Conclusions

23. Bonus Bonus Session on MCP-PMT Lifetime Satuday Jan. 30 9:00-11:30 Comments/Questions/Suggestions: Please see Andrew Brandt (brandta@uta.edu) 23