1. Jornadas do LIP 2012 L. Pereira 1 Gaseous Anger Camera Emulation An experimental system to study the design and optimization of gaseous detectors with Anger camera readout L. Pereira 1, A. Morozov 1, L. Margato 1, M. M. Fraga 1, F. Fraga 1 1 LIP-Coimbra, Departamento de Física, Universidade de Coimbra, 3004-516 Coimbra, Portugal.

2. Jornadas do LIP 2012 L. Pereira 2 Position sensitive gaseous detectors using Anger type optical readout were used by several groups to detect different types of radiation. ZEPLIN-III which is looking for galactic WIMPs [2] Two-phase (liquid/gas): Xe Photodectors: 31 PMTs GSPC with optical readout for thermal neutrons detection [3] Gas: He 3 + CF 4 detector Photodetectors: 4 PMTs. [1] http://heasarc.gsfc.nasa.gov/docs/sax/instruments/parmar_etal_AaAS.html [2] http://www.hep.ph.ic.ac.uk/ZEPLIN-III-Project/ [3] http://indico.cern.ch/getFile.py/access?contribId=28&sessionId=3&resId=1&materialId=slides&confId=77313 Ex.: The low-energy concentrator spectrometer on-board the SAX X-ray [1] astronomy satellite (1996 - 2003). Gas: Xe. Photodectors: 1 Multi-anode PMT

3. Jornadas do LIP 2012 L. Pereira 3 Gaseous Anger Camera What is the best achievable spatial resolution ? Spatial resolution is a key parameter for any Anger Camera. Distribution of (X, Y) positions with an associated width determining the spatial resolution of the camera

4. Jornadas do LIP 2012 L. Pereira 4 Spatial Resolution Algorithm Arrangement Resolution # detected photons PMTs Photocatode Diam. Uniformity Ang. Of incidence Material Transmission Thicknes s Refraction Dist. PMT-MS # photons/Particle # photons/e - Gain Spectrum Window Gas Pressure

5. Jornadas do LIP 2012 L. Pereira 5 3 D Positioning system An experimental system to study the design and optimization of gaseous detectors with Anger camera readout The experimental system should allow to:  Control the geometric parameters of the detector.  Emulate the scintillation in a controllable way.  Develop and test position reconstruction algorithms such as Maximum likelihood, Gradient LS and Neural Networks.  Experimentally evaluate the performance of ANTS [4].  To establish the limit resolution of the detector. [4] A. Morozov et al. D.O.I.: 10.1109/NSSMIC.2011.6154618

6. Jornadas do LIP 2012 L. Pereira 6  SWIP AG, Switzerland: Ø0.5 mm, alumina spheres (Al 2 O 3 ) (Ø 250 μm drilled blind hole, 200 μm deep ) [5].  Use the Henderson method to produce spherical light diffuser [5]. Proposed solution: LED + Optical Fiber + Spherical Diffuser Available options for a submilimetric spherical diffuser: Light source main specifications:  Emitting volume should small (i.e. diam. < 1 mm).  Isotropic. In photodynamic therapy small catheter with spherical diffusers tips are used as light sources or as a light detectors [5]. [5] Hugo J. Van Staveren, Lasers in Medical Science 1995, 1 O: 137-147

7. Jornadas do LIP 2012 L. Pereira 7 1.The Optical Fiber is immersed in Helioseal (dental sealant) [6]. 2.A spherical diffuser is cured with blue light (~ 470 nm); 3.Washed in methanol; 4.Stabilized with paraffin; 5.It’s hard cured with intense blue light; The Henderson method [6] http://www.ivoclarvivadent.com/en/competences/composites/professional-care/helioseal

8. Jornadas do LIP 2012 L. Pereira 8 The light source design  Robust  Simple Ø5mm λ ~ 470 nm LI ~ 6000 mCd Ø 5mm hole 200 μm core F.O. Aluminum Foil Heat shrink tubing Diffuser Formation time for 1 mm diam. diffuser ~ 45 s

9. Jornadas do LIP 2012 L. Pereira 9 Isotropy Diffuser diam. ~ 800 μm Angular Res. = 5º Azimuth = 0º I ~ 20 mA D Dif - PD = 6 cm An isotropy of 10% or better is obtained in at most 1 out of 10 diffusers produced. I(theta, phi = 0)

10. Jornadas do LIP 2012 L. Pereira 10 Simulation with ANTS using experimental values for I(theta, phi)  4 PMT  Active diameter = 36 mm  PMT center to center = 39 mm  1000 Neutrons  Center of gravity  2.5E4 photons/Neutron in 4π ActualPunctual SourceSigma PSDiffuserSigma D X, μm0392154405 Y, μm02398-38399 X, μm750077573627822350 Y, μm-7500-7781357-7774359

11. Jornadas do LIP 2012 L. Pereira 11 Next step  Mount a simple 4 PMT acquisition system to test the concept experimentally.

12. Jornadas do LIP 2012 L. Pereira 12 END