1. Peyrej @ ipno.in2p3.fr Orsay - October 2007IPNO-RDD-Jean Peyré1 Test Protocole for Crystals with Gamma Sources Jean Peyré Oct 2007

2. Peyrej @ ipno.in2p3.fr Orsay - October 2007IPNO-RDD-Jean Peyré2 General requirements Each prototype has to be tested in real condition, i.e.: The crystal has to be close to the one described in slide#3 1.One of the main challenge is to be able to collect correctly all emitted light. So results have to be given with such crystal associated with a detector that does not exceed the shadow of the crystal 2.For example, crystal of exit face 10x10mm measured with photodiode of active surface 10x10mm but of greater package as well as Crystal of exit face 40x20mm neasured with PMT of diameter 60mm is not acceptable) The prototype study has to include the technology feasability of the choosen photodetector, i.e.: 1.For systems that require cooling or temperature stability, the demonstrator will have to include a “cold” technology similar to the one that will be used in final calorimeter 2.For systems that have a sensibility to magnet field, study and tests with Magnet Field must be conducted The tests can be steered in 2 steps: 1.Test of a single Crystal 2.Test of an array of 18 Crystals or a sufficient number to study the board effects (mechanics, cooling, magnetic field, multihit detection in several crystals, influence of thickness of matter between Crystals,…………)

3. Peyrej @ ipno.in2p3.fr Orsay - October 2007IPNO-RDD-Jean Peyré3 Size of Crystal Size of crystal should be close to the one designed for Calorimeter, i.e. detection length of about 110mm, polar angle close to 2 degres, azimuthal angle of 5.625 degres. The crystal can be longer in order to create a light guide adapted to the photodetector (APD, Pin diode or PMt)

4. Peyrej @ ipno.in2p3.fr Orsay - October 2007IPNO-RDD-Jean Peyré4 Gamma source The use of 137 Cs and 60 Co sources is of great interest. 1.Peak at 662 keV of 137Cs source is a reference that you ofen find in articles 2.Peak at 1.17 MeV of 60 Cs source is close to the peak of the goal that has been assigned to those detectors: 5% resolution FWHM at 1 MeV Measurements for 3 peaks at 662keV, 1.17MeV & 1.33MeV 137 Cs peak 0,662 MeV 60 Co peaks 1.17 MeV 1.33 MeV

5. Peyrej @ ipno.in2p3.fr Orsay - October 2007IPNO-RDD-Jean Peyré5 Crystal Gamma source The gamma sources must be collimated. A good compromise is to use a lead collimator (example 5cm thick) with a hole of 4 mm. The distance between the lead collimator and the crystal has to be smaller than 4 cm. In this way, the “stain” made by the source will be approximitly of 7-14 mm depending of the source material repartition in front of the hole. This detail is of great importance, because the homogeneïty along the crystal can be artificially better than reality if the source sprays a too great surface for a given experience. Source Photodetector Lead collimator Movement of collimator along the Crystal

6. Peyrej @ ipno.in2p3.fr Orsay - October 2007IPNO-RDD-Jean Peyré6 Front-End Electronics 1.Use of Charge PreAmplifier + shaper with peaking time of 3 μs 2.Feedback Capacitor C f adapted to the gain of photodetector 3.R f x C f >> shaping time 4.R f >> 1 MΩ to minimize noise 5.PreAmplifier Rise Time T=C d /w c *C f (be careful for LaBr3+APD) 6.Be aware that Front-End Electronics is never saturated and always adapted in gain to emitted light Cd C f & R f feedback capacitor and Resistor C d capacitor of Detector w c Gain Bandwidth product

7. Peyrej @ ipno.in2p3.fr Orsay - October 2007IPNO-RDD-Jean Peyré7 Test of one Crystal Following previous recommendations, the source will move along X and Z axis. For each point, resolution and quantity of collected light with be noted. A plot for both Resolution and Collected light will be drawn Crystal Photo detector x z

8. Peyrej @ ipno.in2p3.fr Orsay - October 2007IPNO-RDD-Jean Peyré8 Test of an array of Crystals The measurements will be made following previous recommendations. The source will interact first with a “central” crystal to be able to study the response of the whole array of crystals. This test will be valid only if a unique crystal meets the requirement of 5% resolution FWHM at 1 MeV Gammas. Collimated source Photo detectors x