7 th AGATA week

Transcription

1 Pär-Anders Söderström Nuclear Structure Group Department of Physics and Astronomy Uppsala University 7 th AGATA week

2 Outline 1 Requirements and Reactions Event generator Geant4 Tracking 3 4

3 Reactions The aim is to find a suitable reaction for measuring position resolution of one triple cluster in the phase at LNL. The idea is to compare FWHM of the γ-ray peaks at different distances. Wtot = Wint + Wrec + W θ

4 Requirements Reactions High v/c High γ-ray energy Narrow angular and energy distributions of recoils High peak count rate Well defined source location - life times of excited states

5 Requirements Reactions High v/c High γ-ray energy Narrow angular and energy distributions of recoils High peak count rate Well defined source location - life times of excited states

6 Requirements Reactions High v/c High γ-ray energy Narrow angular and energy distributions of recoils High peak count rate Well defined source location - life times of excited states

7 Requirements Reactions High v/c High γ-ray energy Narrow angular and energy distributions of recoils High peak count rate Well defined source location - life times of excited states

8 Requirements Reactions High v/c High γ-ray energy Narrow angular and energy distributions of recoils High peak count rate Well defined source location - life times of excited states

9 Studied reactions Reactions Reaction E beam E γ v/c σ H( 37 Cl, n) 38 Ar 75 MeV 168 kev 6.4 % 300 mb H( 51 V, n) 5 Cr 0 MeV 1434 kev 6.4 % 150 mb 9 Be( 80 Se, 3n) 86 Sr 0 MeV 77 kev 6.9 % 300 mb H( 81 Br, n) 8 Kr 40 MeV 44 kev 7.8 % 80 mb 9 Be( 136 Xe, 3n) 14 Ce 470 MeV 641 kev 8.1 % mb

10 Event generator evapor Geant4 MGT Event-by-event data is obtained from the program evapor (PACE). Fusion-evaporation code that evaporates particles up to 6 Li with monoenergetic and Doppler shifted γ-rays added E 86Sr (MeV) θ 86Sr (deg) Example of the the recoil energy and angular distributions in the reaction 9 Be( 80 Se, 3n) 86 Sr.

11 Geant4 simulation evapor Geant4 MGT AGATA demonstrator simulation with Enricos Geant4 program. One triple cluster positioned at 90 degrees from the beam direction. Four different distances to front face of the detector: 40 mm, mm, 140 mm and 35 mm.

12 Geant4 simulation evapor Geant4 MGT AGATA demonstrator simulation with Enricos Geant4 program. One triple cluster positioned at 90 degrees from the beam direction. Four different distances to front face of the detector: 40 mm, mm, 140 mm and 35 mm.

13 Geant4 simulation evapor Geant4 MGT AGATA demonstrator simulation with Enricos Geant4 program. One triple cluster positioned at 90 degrees from the beam direction. Four different distances to front face of the detector: 40 mm, mm, 140 mm and 35 mm.

14 MGT 40 mm, Smearing 5 mm 3 evapor Geant4 MGT E γ (kev) Tracking done with MGT, intrinsic energy resolution assumed to be a FWHM of kev at 1.33 MeV and 1 kev FWHM for noise. 40 mm, Smearing 5 mm 3 No ancillary detectors gives recoils in 0 degrees and average v/c for each event E γ (kev)

15 MGT 40 mm, Smearing 5 mm 3 evapor Geant4 MGT E γ (kev) Tracking done with MGT, intrinsic energy resolution assumed to be a FWHM of kev at 1.33 MeV and 1 kev FWHM for noise. 40 mm, Smearing 5 mm 3 No ancillary detectors gives recoils in 0 degrees and average v/c for each event E γ (kev)

16 MGT 40 mm, Smearing 5 mm 3 evapor Geant4 MGT E γ (kev) Vary position smearing parameter from 1 mm to mm in steps of 0.5 mm. Same value for packing. 40 mm, Smearing 5 mm 3 Energy dependent smearing turned off E γ (kev)

17 MGT 40 mm, Smearing 5 mm 3 evapor Geant4 MGT E γ (kev) Vary position smearing parameter from 1 mm to mm in steps of 0.5 mm. Same value for packing. 40 mm, Smearing 5 mm 3 Energy dependent smearing turned off E γ (kev)

18 Estimation of position resolution p = 1 ( E k close Efar ) ( 1 dclose 1 ) 1 dfar (1) (See previous talk by A. Gadea) Position resolution only dependent on measured FWHM, no dependence. Possible source of error: How to estimate d = d(θ, E γ )? Two sources of uncertainties in d. Geometrical uncertainties and interaction depths.

19 Estimation of position resolution p = 1 ( E k close Efar ) ( 1 dclose 1 ) 1 dfar (1) (See previous talk by A. Gadea) Position resolution only dependent on measured FWHM, no dependence. Possible source of error: How to estimate d = d(θ, E γ )? Two sources of uncertainties in d. Geometrical uncertainties and interaction depths.

20 Estimation of position resolution p = 1 ( E k close Efar ) ( 1 dclose 1 ) 1 dfar (1) (See previous talk by A. Gadea) Position resolution only dependent on measured FWHM, no dependence. Possible source of error: How to estimate d = d(θ, E γ )? Two sources of uncertainties in d. Geometrical uncertainties and interaction depths.

21 Estimation of position resolution p = 1 ( E k close Efar ) ( 1 dclose 1 ) 1 dfar (1) (See previous talk by A. Gadea) Position resolution only dependent on measured FWHM, no dependence. Possible source of error: How to estimate d = d(θ, E γ )? Two sources of uncertainties in d. Geometrical uncertainties and interaction depths.

22 Geometrical uncertainties d (mm) θ d=35mm (deg) The curvature radius of the clusters is designed for d = 35 mm. If the front face of the detector is closer to the source, the distance can vary a lot.

23 First interaction point Histograms from the Geant4 output. Includes both the geometrical uncertainties and uncertainties due to the interaction depth. 40 mm h Entries 8874 Mean 76.5 RMS Interaction distance (mm) 35 mm h Entries 591 Mean 68.3 RMS Interaction distance (mm)

24 First interaction point Histograms from the Geant4 output. Includes both the geometrical uncertainties and uncertainties due to the interaction depth. 40 mm h Entries 8874 Mean 76.5 RMS Interaction distance (mm) 35 mm h Entries 591 Mean 68.3 RMS Interaction distance (mm)

25 FWHM vs. smearing FWHM against MGT smearing for 37 Cl and 51 V beams at 11 cm. Target effects, cross sections and similar carefully studied by Ali Al-Adili and under control. See his masters thesis (in preparation) for details.

26 FWHM vs. smearing (%) FWHM/E γ mm 9Be(80Se,3n)86Sr H(81Br,1n)8Kr 1 9Be(136Xe,3n)14Ce (%) FWHM/E γ 1. 9Be(80Se,3n)86Sr 40 mm mm mm 35 mm MGT Smearing (mm) MGT Smearing (mm) The three reactions looks qualitatively very similar. Example with MGT smearing of 5 mm: 80 Se gives W rec 3.74 kev, W int 1.86 kev 136 Xe gives W rec.89 kev, W int 1.39 kev. As expected, slope change with d. Why do they not meet at 0? Because of packing of 1 mm?

27 FWHM vs. smearing (%) FWHM/E γ mm 9Be(80Se,3n)86Sr H(81Br,1n)8Kr 1 9Be(136Xe,3n)14Ce (%) FWHM/E γ 1. 9Be(80Se,3n)86Sr 40 mm mm mm 35 mm MGT Smearing (mm) MGT Smearing (mm) The three reactions looks qualitatively very similar. Example with MGT smearing of 5 mm: 80 Se gives W rec 3.74 kev, W int 1.86 kev 136 Xe gives W rec.89 kev, W int 1.39 kev. As expected, slope change with d. Why do they not meet at 0? Because of packing of 1 mm?

28 Position resolution vs. smearing Graph Position resolution (mm) 0 40 mm mm Be(80Se,3n)86Sr H(81Br,1n)8Kr 9Be(136Xe,3n)14Ce Graph Position resolution (mm) 0 9Be(80Se,3n)86Sr mm mm 16 mm - 35 mm MGT Smearing (mm) MGT Smearing (mm) The good news: The three different reactions give the same position resolution when run at the same distance. The bad news: The two different distances do not give same position resolution for the same reaction. Possibly related to uncertainties in d?

29 Position resolution vs. smearing Graph Position resolution (mm) 0 40 mm mm Be(80Se,3n)86Sr H(81Br,1n)8Kr 9Be(136Xe,3n)14Ce Graph Position resolution (mm) 0 9Be(80Se,3n)86Sr mm mm 16 mm - 35 mm MGT Smearing (mm) MGT Smearing (mm) The good news: The three different reactions give the same position resolution when run at the same distance. The bad news: The two different distances do not give same position resolution for the same reaction. Possibly related to uncertainties in d?

30 The method proposed by F. Recchia seem to work with simulations Necessary to find a way to determine d with good accuracy Reaction rate example: 80 Se, 1 pna, 1 mg/cm, 300 mb gives about 500 Hz in peak Requirements - OK