1. A gas scintillation proportional counter for thermal neutron scattering measurements D.Raspino, N.J.Rhodes, E.M.Schooneveld (ISIS-STFC), I.Defendi, M.Jurkovic, K.Zeitelhack (FRMII-TUM), F.A.F.Fraga, L.M.S.Margato, A.Morozov, L.Pereira (LIP Coimbra), B.Guerard, G.Manzin, H.Niko, A.Gongadze (ILL), R.Engels, G.Kemmerling (Jülich GmbH) and F.Sacchetti (INFN).

2. Outline Aim of the project Detector description Results –Position resolution Electronics Conclusions

3. The Project NMI3 – FP7 collaboration – 2009-2012 Six European institutes: FRM II, ILL, ISIS, Julich, LIP, INFN Develop a 2D detector for thermal neutrons with: –Position resolution < 1 mm –Efficiency > 50% for 1 Ǻ –Active area of 200x200 mm 2 –Rate capability ~1 MHz Application in the neutron scattering community in: –Reflectometry –SANS (micro-focusing) Gas Scintillation Proportional Counter (GSPC)

4. The Detector PMT MSGC ~4.5∙10 5 γ /n at G~10 2 Transparent Mesh (~ 5 kV) Transparent Window n (E 0 ) 3 He-CF 4 (~6 bar) 3H3H p γ PMT PMT signals ANTS: Anger-camera type Neutron detector: Toolkit for Simulations http://coimbra.lip.pt/~andrei/ A. Morozov et al, 2012 JINST 7 P02008. 1 cm

5. The MSGC Produced by IMT Glass: Schott S8900, 1 mm thick Strips: –Chromium.5 µm thick –Anode pitch: 500 µm –Anode width: 5 µm –Cathode width: 200 µm All anodes connected together All cathodes connected together Active area: 32x32 mm 2 / 90x77 mm 2 at 6 bar CF 4

6. The PMTs signals PMTs signals digitised at 400 MHz – 12 bit Signals are filtered τ =150 ns Amplitude (a n ) at the peak of the signal is measured for each PMT The 2D position of the neutron is calculated using the Centre of Gravity (CoG) of the light 7 PMTs in hexagonal arrangement Raw signals

7. Position Resolution Four PMTs (Ø=38 mm) in a square array PMTs to MSGC  20 mm 1 bar 3 He / 2 to 6 bar CF 4 Gain increased until not better position resolution Similar results with 7 PMT (Ø=29 mm) in hexagonal arrangement 3H3Hp

8. Electronics ADC FPGA DSP Peak Finder γ /n Position X,Y PH

9. Position Reconstruction Algorithms PMTs signals amplitudes as input  XY as output Centre of Gravity (CoG) Maximum Likelihood (ML) Least Square (LS) Neural Network (NN) Position Resolution FWHM (mm) COGMLLSNN 0.80.83 0.82 Cd Mask Holes 2 mm Ø, 5 mm pitch

10. Gamma/neutron Σ PMT signal Charge signal n PMT signal charge signal γ PMT signal charge signal Reason for slower gamma signal: Electron ionises much large volume of gas than proton + triton  Takes longer for all charges to drift to MSGC  Gamma signal is wider (and lower).

11. Full size detector 40 x 40 cm Al vessel fill pressure: 1 bar He + 7 bar CF 4 Entrance Al window (5 mm) MSGC S8900 (9 cm x 7.3 cm) 3.3 mm Borofloat glass window 19 R5070A PMTs on 28.5 mm pitch Tested up to 400 kHz incident rate Read out with the final electronic  x = 0.60 mm

12. Conclusions The GSPC was developed in the NMI3-FP7 project The obtained performance are the result of the precise measurements of the detector’s physical parameters The simulation tool (ANTS) has been crucial for the development of the detector: –Position reconstruction –Position resolution –Rate Capability A real size detector is operative Future Try the detector on a reflectometer

13. Light Spectrum A. Morozov, L.M.S. Margato, M.M.F.R. Fraga, L. Pereira, F.A.F. Fraga, Secondary scintillation in CF 4 ; 2012 JINST 7 P02008. Red PMTs S20 photocathode Fused Silica Window 200-800 nm QE~10% Blue PMTs Bialkali photocathode Borosilicate Window 300-550 nm QE~20%