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Background Measurement: December 2011

Background Measurement: December 2011. Spring Test. Thomas E. Videbaek Stony Brook University, RHIG. Thomas K Hemmick Stony Brook University, RHIG. Outline:. Reminder: HBD Principle. Goals. December experiment: Run conditions Data Scintillator Data Neutron rates

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Background Measurement: December 2011

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  1. Background Measurement:December 2011 Spring Test Thomas E. Videbaek Stony Brook University, RHIG Thomas K Hemmick Stony Brook University, RHIG SoLID Collaboration Meeting 2/3/2012

  2. Outline: • Reminder: HBD Principle. • Goals. • December experiment: • Run conditions • Data • Scintillator Data • Neutron rates • GEM detector rates and spectra • March test plans: • Rings • Tracks • EMC • TOF • Offline software SoLID Collaboration Meeting 2/3/2012

  3. g HV primary ionization photo electron charged particle or photon HV primary ionization e- HBD Principle Reverse Bias (HBD) Forward Bias Mesh CsI layer Triple GEM Readout Pads Readout Pads • BRIGHT! ~20 photo-electrons in 50 cm of gas: • Principle source of photons at LOW WAVELENGTH! • dN/dl ~ 1/l2 • QE falls linearly as l increases. • Single electron gain ~104(a bit limited by the CsI). • You can see a blob…single p.e. difficult. • More GEMs = higher gain…BUT there is a cost in hadron blindness.

  4. Target Ed ~0.1 kV/cm Hadron Blindness:UV photons vs charged particles • At slightly negative Ed, photoelectron detection efficiency is preserved whereas charge collection is largely suppressed. • Charge collected from ~150μ layer above top GEM AND the gaps between GEMs. • With n GEMs, reverse bias suppresses hadron gain from Gn to Gn-1

  5. Three Birds with One Stone • EIC & sPHENIX: • Develop CsI technology to measure rings. • Mirror technology. • Precision position measurement via charge division. • REQUIRES HIGHER GAIN! • SoLID • Threshold detector using mirror. • Less sensitive to neutron and low-E gammas. • Test Program: • December: Background measurement. • Spring: RINGS! SoLID Collaboration Meeting 2/3/2012

  6. December Goals: • How fast does a scintillator fire in the Hall? • What are the rates of neutrons (fast & slow)? • How quickly does our GEM detector fire? • Will we be able to see single photoelectrons? • What stack size will provide best conditions for running in March? • What is the degradation of hadron blindness for large numbers of GEMs? • Triple, Quadruple, Quintuple stacks. SoLID Collaboration Meeting 2/3/2012

  7. Simpler “November” Apparatus?? “DECEMBER” • CsIGemstack in CF44 • Pad readout (~50 channels) • Are THICK (1/2” SS) walls an issue? • Is this viable?

  8. Experimental Setup • High purity recirculating gas • ~1 ppm H2O & O2 • CAMAC DAQ • LeCroy High Voltage • GEM detector • Divider box allows for 'on the fly' stack size changes • Neutron Counters • BF310B + n  7Li + 4He • Bare counter (slow) • Wax counter (slow & fast) • Scintillators SoLID Collaboration Meeting 2/3/2012

  9. DAQ – dead simple • PC in the Hall • Remote desktop allows: • HV via serial port. • CAMAC via USB • USB CAMAC controller. • NIM Trigger: OR from the scintillators, three of the GEM pads, and either of the neutron counters. • Digitized trigger signals to provide a mask for the data. SoLID Collaboration Meeting 2/3/2012

  10. Run conditions in Hall A • Average beam current held around 1 microA for most of our runs • Some were taken at 20nA or 100nA. • Collection rates much slower, usually. • Depending upon the tune of the beam (either on target, hitting target holder, calorimeter run, etc.) background rates varied dramatically. • Anywhere from 1Hz to 1kHz. SoLID Collaboration Meeting 2/3/2012

  11. Scintillator Data • When we first turned on our phototubes, we saw7 million triggers in less than a minute. • Upon viewing data, could not parse the file. • Turned HV off phototubes for the rest of the runs. SoLID Collaboration Meeting 2/3/2012

  12. Neutron Data: Beam on Target Rate from typical on target run: Wax • Bare Neutron Counter shows few, if any, counts while beam is on target. Some runs show rates of ~0.6 Hz. • Average rate for Fast and Slow neutrons ~34.75 Hz. • Ratio of rates ~58. • Counter sensitivity: 1.9 cps per thermal neutron/cm2/sec SoLID Collaboration Meeting 2/3/2012 Rate from typical on traget run: Bare

  13. Neutron Data: Beam Off-Target Rate from a calorimeter run: Wax • Rate for Fast and Slow neutrons ~1.6 kHz. • During the tuning or calorimeter runs, the rates increase, but the ratio should remain constant. • Ratio of rates is ~35 on average. • Implies Slow neutrons are produced more during off target (i.e. striking collimators etc…) conditions. SoLID Collaboration Meeting 2/3/2012

  14. Neutron Rates • Wanted a plot of neutron rate vs. beam current, unfortunately we had a low number of records for low beam current. • Also lot of off target data. • Rough fit:~0.11 Hz/nA or ~0.06 therm-n/cm2/sec SoLID Collaboration Meeting 2/3/2012

  15. GEM Detector: Hadron Blindness Legend: Blue = +40 V Teal = +20 V Pink = 0 V Green = -20 V Red = -40 V • As the stack has few GEMs, you are able to achieve a better hadron blindness. • This is because ionization can occur in the gap between the first and second GEM. • For fewer GEMs we were unable to get small signals above the hardware threshold.  SoLID Collaboration Meeting 2/3/2012

  16. GEM Detector: Presence of MIPs • When the difference is taken between the forward-most and reverse-most bias, one should see MIPs. • Best for fewer GEMs via the Gn-1 principle. • Normally we expect ~15 p.e. for 1.5mm of CF4. • Here tracks are inclined ~17o above horizontal. • 15/sin(17) ~ 50….SWEET! SoLID Collaboration Meeting 2/3/2012

  17. GEM Detector: Threshold Rate • Rates of the different stacks as a threshold of primary electrons falls off rapidly. • For 5 stacks, rate ~0.1 Hz/nA with 0.5 p.e. threshold… SoLID Collaboration Meeting 2/3/2012

  18. GEM Detector: Neighbors • Finally, we looked at the response of trigger pads only when a neighboring pad fired as well. • Idea is that Cherenkov blob would fall on multiple pads more often than electron clouds from hadron. • Analysis not finished, but rates cut DRAMATICALLY! SoLID Collaboration Meeting 2/3/2012

  19. Spring Test: Point at Target. • “Beam” consists of scattered electrons & pions. • Particles must be collimated. • Need to “point” detector at target. • Slide jack post back&forth via remote control. SoLID Collaboration Meeting 2/3/2012

  20. Small Table Layout • All aboard! • Quintuple GEMstack (can always “shrink”). • Need trackers to know each particle’s trajectory. • PbGl is used to identify electrons (enough???) • Bore site laser of initial alignment. • Coarse pads in case scintillators fire too fast. • MRCP—why not? (TOF PID!!!) SoLID Collaboration Meeting 2/3/2012

  21. Cherenkov Optics • Optics defined by GEM size (Rring < 5 cm). • Rad-length for SoLID perfect fit for optics! • Should see 20 p.e. or more. • NOTE: Not all rings will be fully contained. SoLID Collaboration Meeting 2/3/2012

  22. VUV Mirror Interference Maximum • Require mirror reflectance DEEP in the VUV. • Ordinary MgF2 cutoff l<140nm. • Overcoat thickness = thin film reflection max! • Test Beam: Acton Optics • Future: Make our own 8’ diameter vessel SoLID Collaboration Meeting 2/3/2012

  23. Pad Segmentation • RING images produce POSITION CORRELATION! • Ambiguity for Compass (Cartesian) Coordinates • SOLN: New pad plane • ¼ rings in four quadrants • STAR-style strip-pixels. Pad Plane Arrives Monday SoLID Collaboration Meeting 2/3/2012

  24. DAQ: SRS (w/ cheats!) • MUST get aux detectors into data stream. • SRS does not work & play well with others. • SBU pad plane sends 8 input channels of APV25 cards to LEMO connectors. • Choosing the resistors & capallows any signal to coupleinto datastream. • MRCP: Use a TAC • Desire custom LEMOAPV25 card(s) SoLID Collaboration Meeting 2/3/2012

  25. Pattern Recognition • Require ONLINE Tracking (to find target). • HuijunGe writing “light environment”. • Must run “out of box”. • No dependences except root. • FRODO (son of AVATAR): • Singleton factory for context independent access. • STL vectors of simple objects: • Strips; PadStrips; Blobs; Clusters; • ALL objects can be drawn to root canvas (EVT DISPLAY) • URGENT: NEED TO UNDERSTAND SRS FILE FORMAT! SoLID Collaboration Meeting 2/3/2012

  26. MINIMUM: 1 day running -Magnet off -Magnet orientation=0 Rates SoLID Collaboration Meeting 2/3/2012

  27. Summary • Success depends upon multiple factors: • Sufficient beam time & conditions. • Reliable & Homogeneous DAQ • Multi-institutional efforts: • SBU, U.Va, J-Lab, Temple, Duke. • Online pattern recognition & tracking • Also depends upon: • Clean gas, high QE cathode, high/stable gain, accurate alignment, phase of the moon. • Schedule: • Last critical part (mirrors) arrive ~March 1. • Kondo & Kiad SBU @ this time. • Delivery to hall  Ides of March SoLID Collaboration Meeting 2/3/2012

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