Detector issues in the New Experiment: D. Hertzog

1. Detector issues in the New Experiment:D. Hertzog • Basic idea of measurement • Review method from E821 • Sedykh et al, NIM A 455 (2000) 346 • Two complementary analysis streams: Q and T • Status of new W / SciFi design • Some slides from earlier on • Electronics implications • DAQ • Budget

2. NA2 2.5 ns samples N A <A>=0.4 An “event” is an isolated electron above a threshold. Higher rate exacerbates pileup & gain stability issues e+ Lab Frame N, A and NA2

3. The Flash and Neutron Concerns • Neutron-induced pedestal rise falls with over many 10’s of ms • Data recorded on “islands” of waveform samples with 2.5 ns binning

4. Some features of our calos • Pb/SciFi matrix • Resolution at 2 GeV was about 6.8% (all factors included) • 4 lightguides and PMTs from 1 calo • Energy summed into one signal • Doped for neutron “immunity”

5. Example data spectrum from ring

6. CALO X hodoscope e+ The high rate at injection and the flash-induced background were severe design constraints • E821 Instantaneous rates: • At ~25 ms after injection, E > 1 GeV: Each calo sees about 0.9 MHz • With “no” threshold, the rate is about 1.8 MHz • New Experiment Challenge: • Higher rates • How to manage pileup and keep average rate on PMTs “low”? • Detector response: fast scint • Pulse-to-pulse separation ~ 4-5 nsec • Gated off for 10’s of ms was required • Back on in 1 ms to 99.9% of gain • Stability of gain a challenge • Pileup algorithms clever, • But, 0.08 ppm systematic remained from percent-level pileup

7. 16 cm 12 cm 20 cm Strategy is to segment longitudinally and increase density (decrease Moliere radius) • Without a long discourse here on why* we arrive at • Tungsten-SciFi-Ribbon Calo • Energy resolution determined by W/SciFi thicknesses and ratio 40 layers of 0.5 mm W and 0.5 mm scintillator fiber ribbons, each 4 x 12 cm Res vs layer thickness

8. A key design consideration is multiple shower resolution … including proper partitioning of the respective energies • When showers are simply “close” in time, the problem is “easy” • But if the showers overlap, the only option is spatial separation … • Our goal: resolve 2 hits 80% of the time • ACHIEVED in this design (simulation) • Even though, the non-uniform hit distribution exacerbates pileup Radialprofile  Muon orbit Verticalprofile

9. Electrons from g-2 ring strike calo at energy-dependent angle. T/he energy vs. average striking angle

10. Another consideration: positron entrance angle depends on energy: low-E showers are “wider” TOP DOWN VIEW And the “calibration” depends on angle High E Low E m central radius vacuum

11. Implementation issues: guides and constraints • System fits in available space • We know how to build and cost it • Calibration and gain stability • Laser distributed to each PMT • Beam with entrance coordinates known • PMTs good but not exotic in requirements • Bases still require a gating circuit PMT box

12. A prototype of one sub-module has been built and tested • W / fiber ribbon layers, 0.5 mm thick • 6 cm wide; 4 cm high • Real blocks will be made as one large, complete detector Stacking Gluing Machining Polished end

13. W/SciFi Fits

14. Resolution (data vs MC)

15. Moliere radius is 20 mm (simulation)

16. Longitudinal shower development leads to confirmation of radiation length of 7.7 mm

17. Latest thoughts … • Could readout with new large-area SiPM (APDs in Geiger mode) • Fast, good QE, immune to magnetic field • Could reconsider lead tungstate crystals that are “faster” … as at PANDA and Mu2e (synergy)

18. A front segmented detector (FSD) is used for beam vertical alignment, calorimeter calibration and shower characterization, and muon loss monitoring • Default technology is standard segmented hodoscope with 10 PMTs • Alternatives (slide in reserve)

19. High-rate u-v wire chambers will also work • Allows useful calibration runs centered on blocks (x) and centered between them (x) x x u-v wire chambers 63 pixels (convenient) A front segmented detector (FSD) is used for beam vertical alignment, calorimeter calibration and shower characterization, and muon loss monitoring • Default technology is standard segmented hodoscope with 10 PMTs • But pixel detector patterns and technologies being investigated • This will not drive the cost at all

20. Geant with proposed W/SciFi geometry T Method Same GEANT simulation Q Method Two complementary methods of determining wa • “Q” (charge) integrates energy in whole calorimeter vs. time • no event recognition necessary • no pileup • asymmetry lower • systematics different • “T” (time or traditional) selects pulses above Eth • bin events vs time • well understood method • smallest wa uncertainty

21. Conclusions • Main challenge for E969 is higher rate and greater data volume (per stored event) • Solved by “pushing” but not “inventing” technical component methods • Calo, FPD, WFD, DAQ, offline • Systematics improved by T and Q methods of data analysis and by complete data stream information • Pileup methods much cleaner • Hardware budget for these small compared to other parts of proposed budget • … but it hides the significant University labor pool contributions: • Professors, Senior Scientists, PDRAs, Grad. Students, Undergrads, Technicians, subsidized Engineers

22. Labor UIUC University techs 1.5 man years “free” Includes real engineering University students and PDRAs Budget bottom line* • Calorimeters (500 channels) • PMTs** $125k • Bases $ 50k • Tungsten: $155k • Fiber ribbons: $500k • Guides materials and vendors $ 50k • Mechanical supports (mostly labor) $ 25k • Front Segmented Detector • Scintillator version (250 ch) ** $250k • Electronics • WFDs $450k • Clocks; misc $ 50k • VME crates + interfaces $220k • DAQ • Frontend computers $ 68k • Tape drives + slow control $ 62k • Tapes media $125k • Mini Offline • Small local farm $100k • BOTTOM LINE $2230k * The intention is that the bulk of this is funded through DOE and NSF University programs ** Not factoring in reuse of >150 PMTs and bases from E821

23. Electrons strike calo at energy-dependent angle. This affects segmentation consideration The average striking angle vs. energy

24. Complete data stream involves “all samples for all segments for all times” • 500 channels • 600 ms spill length • 2 ns sampling (8 bit) • 150 MB / fill - rawdata • 2.400 TB / h - rawdata • ~2500 TB / run - rawdata • Compression to desired data will reduce by x10

25. 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds 20 wfds Data flowcontinuous digitization etc Rate • Total stored ~250 TB for the experiment 640 MB/s or 27 MB/s each F E F E F E F E F E F E F E F E F E F E F E F E F E F E F E F E F E F E F E F E F E F E F E F E 2.7 MB/s to each stream 10 GB/s switch Backend “T” Data Backend “Q” Data T stream is “zero suppressed” Q stream is rebinned without loss of information

26. T and Q streams come from same WFDs and same data stream • Q stream is rebinned without loss of information • T stream is “zero suppressed” • Bottom line: ~250 TB for the whole run • Special remarks • Front-end CPUs, VME crates for each calorimeter station • -- “working” model; likely to change to simpler, cheaper format • Clock distribution exists (solved and implemented in MuLan expt.) • New waveform digitizers, having deeper FIFOs are required • DAQ system modeled on MIDAS, in use by us for 2 high-rate, precision experiments at PSI • mainly scaling up data paths and speeds • challenging, but not beyond doable • use of computer science students has been effective

27. New waveform digitizers must have deep memory and fast readout • 350 channels of 500 MHz, 8-bit WFDs built for MuLan in Fall 2005 • Characteristics that are appropriate for g-2: • Sampling speed • Analog frontend • Flexible firmware • Limitations for g-2: • Cannot store all samples for complete AGS cycle • Readout not fast enough • New version can be scaled from our very recent experience • Production issues: • Engineering ~1 man year to modify design • Parts and construction ~$400/ch • Testing (local, students)