Activities in Mainz

1. Activities in Mainz David Lomidze, Andreas Winhart Universität Mainz MUV working group meeting CERN 15 Dec 2010

2. Investigation of properties of Protvino scintillator using: Cosmics Laser Radioactive Source LED system Automatic test line for mass-test Setup for Prospective PMT test Outline

3. Laser setup Nitrogen Source PM_L PM_R UV Laser Generator Ultraviolet Nitrogen Laser Wavelength 337 nm Mimics p-Terphenyl Light distributor Energy diode Trigger diode Advantage: well defined pulses, fluctuations canceled by energy diode Disadvantages:Low rate (10Hz), Scintillator must be unwrapped Filter Reflector

4. Setup for PMT photo window uniformity y x ~20% fluctuation expected

5. PM surface scan ~20% fluctuation of PMT photo window as expected

6. Sr90 Setup A B T1 St T2 β energy end point 0.5 / 2.3 MeV Sr90 Collimator A&B – Read out PMTs T1&T2 – Trigger PMT St – Trigger Scintillator, 0.5mm Thick Advantages: High rate ~1KHz (High speed for testing) Disadvantages: Difficult for energy calibration, Wide range of energy, because of β spectrum nature

7. Sr90 Spectrum Typical Beta energy distribution Full spectrum of Sr90 Measured beta spectrum, from two different PMT Theoretical Mean value and area under curve can be used as relative estimators for strip quality Experimental

8. Sr90 Collimator (Electron Spectrometer) + - N S Magnet At this moment this is at just an idea, but we will try to realize it! Second Collimating hole Field S N Hole for Magnet Force First Collimating hole Current Sr90 Threshold

9. LED system • Several LED with different wavelengths • 270 μm – to activate p-Terphenyl • 337 μm to mimic Laser • 490 μm to mimic WLS fiber light (for mass test of PMTs) Work in progress on ultrafast LED driver: 1.5ns pulse rise/fall time Variable pulse length (6ns – 200ns) Variable pulse size (few mV to 10V) Variable rate from few Hz up to 100 MHz (for PMT)

10. LED system • There are few ways for long scintillator tests with LEDs: • Put several LEDs under scintillator (Very fast but expensive way (~170€ each LED)) • Drive light from one LED with bundle of clear fibers • Move one LED along scintillator by stepping motor (Bit slow, but low cost way)

11. Automatic line for mass-test Laser Cosmics Trigger

12. Why needed it? Stepping motor controller application needs windows platform and DAQ is running under Linux SLC4 But… IT650Flash controller has 4 bit input port, which can be used for CAMAC TTL signals to control it Extremely high noise - when motor is powered Few power supply filters have been tried unsuccessfully to solve it No noise if motor is disconnected from controller Way out – intermediate box Intermediate box for merging Windows and Linux applications • 24V relies – to disconnect motor before data taking till next movement • Auto operation mode • RS232 serial connector for automatic control by CAMAC – to generate 4 bit signals + one control line to activate/deactivate relies • Manual operation mode

13. While testing of several samples – observed, that coupling can influence measured Nphe Main problem -> sometimes not having same length of free fibers after gluing on each side of scintillator sample (~1/2 mm) To exclude geometrical fluctuations: New PMT mask with holder have been designed New Mask • Features: • Always 90o angle between WLS fiber and PMT Photo Window (PPW) • Keeping end of fibers always at same distance from PPW • Variable distance between fibers ends and PPW

14. Measurement with Laser # of Photo Electrons VS Scintillator length Npe 1900 x 40 x 10 mm3 scintillator sample with two glued fibers X10 cm Lowest signals from central region ~8.3 Photo electrons from single PM But ~16phe from sub-channel and 12x16=192phe longitudinal channel

15. Study of relative light output in WLS fibers using laser • 400 x 40 x 10 mm3 Scintillator sample • One end read-out by 5mm thick plexiglas • Other end by two WLS fibers, glued along strip 90 x 2 = 180 Phe = totalBlue light 12 Phe in two WLS fibers, Green light ~6.6% of light in two WLS fibers

16. Study of relative light output in WLS fibers using laser 90 x 2 = 180 Phe = totalBlue light 12 Phe in two WLS fibers, Green light ~6.6% of light in two WLS fibers (Fiber trapping Efficiency (5-6%) & PMT Quantum efficiency plays significant role) Quantum efficiency ~16% (at 500nm) (~28% at 390nm)

17. Wrapping test Unwrapped Wrapped Light output doubled!

18. Summary table of cosmic test of WLS fibers To confirm those numbers final size of scintillator prototype needed!!! - Npe from single fiber - Npe from all fibers

19. Considered fibers for single channel construction: Single Kuraray or Two Bicron 1.2mm round MC fibers 2XBicron delivers ~40% more light than single Kuraray fiber two fibers are more safe Wrapping – significant improvement for light collection Gluing gives ~50% more Photo electrons Groove size for 1.2mm fiber – 1.5 x 1.6 mm^2 Number of Grooves = 2 MUV1 single channel design

20. Test setup for 1000 scintillator test: Ready with laser Ready with Sr90 full spectrum Laser alternative way – LEDs getting ready LED driver – experts are involved, already have a prototype Put threshold on Sr90 spectrum –work in progress (designed first prototype, needs modifications) MUV1 PMTs test: Laser system ready! LED system in way of development MUV2 PMTs HAC PMTs recently moved to Mainz, quality test will start after New Year Scintillators with final dimensions needed asap! additionally we NEED to have low quality scintillators (bubbles, dust, low or high fraction of scintillation material) to check quality/efficiency of our system Outlook