Dr. Begoña Fernández Martínez, Dr. Alejandro Garzón, Dr. M.A.G. Alvarez, Prof. Joaquín Gómez Camacho
Centro Nacional de Aceleradores (CNA)-University of Seville Collaboration Work with: CEA-Saclay & GANIL
Beam Tracking Detectors & Asociated Electronics
for FAIR and SPIRAL 2
Beams with large energy and angular straggling
Motivation
New facilities like FAIR and SPIRAL2 will provide radioactive ion beams at low energy (<10 MeV/n) and high current (≈106pps)
Tracking detectors: time and spatial information, event by event, to reconstruct the reaction kinematics with minimal disturbance of the beam.
θf
θf θ0
Target Ideal beam
Real beam Tracking detectors
Emissive foil detectors are good candidates: only a very thin aluminized mylar foil (0.9 μm) is placed in beam.
Ion Beam Emissive Foil
Accelerator Grid
E SE
B E
Since 2007 the Basic Nuclear Physics Group of the CNA-University of Seville is working in collaboration with GANIL and CEA-Saclay in R&D on SeD at low pressure for beam tracking.
SED detectors for low energy heavy ion beam tracking
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Several prototypes of SeD at low pressure (~ 6 mbar) with a small active area (7x7 cm2) were constructed and tested:
Wire chambers: miniSED-1D (based on SED detector installed at the focal plane of VAMOS) and miniSED-2D, where the cathode wires is removed and the cathode strips is replaced by a pixellated cathothe (X and Y information)
Micromegas at low pressure: it was the first time that was used a micromegas detector at low pressure in secondary electron detection configuration
Low Pressure Gas iC4H10 at 5.5 mbar Y
X
Structure of miniSED-1D
0.9 μm mylar aluminized + grid
Gas: iC4H10 at 5.5 mbar Micromesh 128 μm amplification gap
28 strips cathodes 4 cm
Driftgap :1 -2 mm
Structure of micromegas at low pressure Pixellated Cathode
MiniSED detector
*J.Pancin et al., JINST 4:P12012(2009) B. Fernández et al., JINST 7 C03017 (2012)
SED detectors for low energy heavy ion beam tracking
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Test and results of miniprototypes with a 252Cf source in laboratory
Characterization of wire chambers with FF source:
•The obtainedtime resolutionwasσt= 110±15 ps(3.2 mm gap) forminiSED-1D.
•The obtainedtime resolutionforminiSED-2Dis comparable to miniSED-1D:σt= 105±20 ps.
•Spatial resolutionwith radioactive source were measured forminiSED-1D and 2D:σS≈0.5 mm.
•Magnetic field mandatory (σx= 1.4±0.1 mm).
Gain and time resolution of micromegas, at low pressure, were studied for different thickness of amplification gap (128 μm, 256 μm and 512 μm). The best result achieved is comparable with wire chambers:σt= 140±40 ps(256μm).
Test at GANIL with ion beam of84Kr+13at 1.76 MeV/n.
Influence of counting rate on time resolution, gain and sparking limit was studied. Best results: σt= 120±10 ps for wire chambers and σt= 140±15psfor micromegas.
A real size prototype of 2D wire chamber at low pressure was constructed: DemiSED
MiniSED-2D presents the best behavior with the counting rates, showing an almost stable time resolution.
SED detectors for low energy heavy ion beam tracking
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•Active area: 200x120 mm2
• 20 μm diameter anode wires in the middle of 3.2 mm gap
•Anode divided in two parts for capacitance reduction
Real Size SeD prototype coupled to a thin emissive foil
• 2D pixellated cathode.
•67(X)+47(Y) cathode strips with 3 mm pitch
•Strongback with 92.5 % transmission to ensure gap thickness homogeneity
DemiSeD: A real size prototype of 2D wire chamber at low pressure
Test and results with a 252Cf source in laboratory:
•The time and spatial resolutions obtained : σt≈ 120 ps and σs≈ 0.6 mm.
• Strong influence, on DemiSED spatial resolution, of the strongback. New strongback design needed!!.
• Study about the homogeneity of the spatial resolution over the surface detectors:
It shows the dependence with the place where the electron clouds hits: the center of the strip or the interstrip.
2D pixellated cathode
SED detectors for low energy heavy ion beam tracking
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Final Detector under construction
SED detectors for FALSTAFF- NFS will be installed next year
FALSTAFF : Four Arm cLover for the Study of Actinide Fission Fragments
IC
Source Emissive foil SEDFrom: D. Doré
Secondary Electron Detectors: SED FNB Line at the CNA
Motivation: Use stable ion beams, from the 3 MV Tandem accelerator, for testing SED prototypes (and nuclear instrumentation in general), at CNA-Seville
• +30° line of the 3 MV Tandem at CNA
• 2 vacuum chambers: reaction chamber and tracking chamber
• Vacuum: 2x10-6mbar
• Flanges with electrical connections
• Gas regulation system at very low pressure
Sevilla, 12 Marzo 2014
Secondary Electron Detectors: SED
Sevilla, 12 Marzo 2014
Beam Test at CNA: Detector Laboratory
Clean zone
Wire plane for the emissive foil
Mylar window construction process
Table to install the detectors, emissive foil, source…
Secondary Electron Detectors: SED Beam Test at CNA: Measurements
Viability study: Set-up
Collimators Collimator
MiniSED
EF Si
detector
Collimator
58Ni ion beam
• Beam: 58Ni @ 36 MeV and 200 pA
• Trigger: coincidence between Si and MiniSED
SE
Secondary Electron Detectors: SED Beam Test at CNA: Viability study
Amplitude comparison between beam and FF source
• Difference in amplitude due to the SE emitted by the EF
• Amplitude signal obtained at CNA comparable to the GANIL one (75 mV vs 85 mV)
Consistence with the idea of testing SED detectors with
stable beams at CNA
84Kr beam at GANIL
58Ni beam at CNA
•Beam: 58Ni @ 36 MeV and 200 pA
•Trigger: coincidence between Si and MiniSED
SEDA PREAMPLIFIER: TEST WITH ALPHA SOURCE AT CNA
SEDA is a Trans-impedance Pre-Amplifier developed by CNA & IMSE (Seville) for secondary electron detectors (PhD Alejandro Garzón):
4 channels per SEDA card
shaping time between 140 and 170 ns
External control of gain by a line receiver module (G=1,2,4,8)
Good signal to noise ratio relation: 100/10
Experimental set-up
αsource collimator
Mini-SED 1D
• Eα≈ 5.5 MeV
• Alpha source in front of the detector
• Detector: MiniSED-1D full of pure isobutane at 7 torr
• Collimator placed at 1 cm from the miniSED entrance window
•1.5 mm Ø collimator hole
•No B field applied
SEDA PREAMPLIFIER TEST WITH ALPHA SOURCE AT CNA
Anode signal
Cathode signals with SEDA
Signals view on the oscilloscope
Test results
Multiplicity histogram
Spatial resolution result
σ= 1.3 mm
B.Fernández
SPATIAL CHARACTERIZATION OF MINISED COUPLED TO SEDA PREAMPLIFIER AT CNA
Signals view on the oscilloscope
B.Fernández Anode
signal Cathode signal
with SEDA
Experimental Set up
Measurements conditions:
•Beam 58Ni @37.5 MeV
•Study performed changing detector polarization and isobutane pressure
Spatial resolution analysis applying baricenter method: calculate the geometric center of gravity of the charge measured in some strips
SPATIAL CHARACTERIZATION OF MINISED COUPLED TO SEDA PREAMPLIFIER AT CNA
B.Fernández
Multiplicity: How many strips have signals??
Results:
Spatial resolution without magnetic field
σ = 1.2 mm
SPATIAL CHARACTERIZATION OF MINISED COUPLED TO SEDA PREAMPLIFIER AT CNA
Results:
RUN
PMS (torr)
Ehaz (MeV)
I MS (nA)
V MS
(mV) Multiplicity Qsum Qmax σ (mm) FWHM Cathodes
88 8 37 19 600 7.1 3479 1371 1.2 2.86 X
117 8 30 19 600 7 4043 1368 1.77 4.2 X
118 8 30 12 580 5.6 2493 883 1.67 3.93 X
128 8 30 8 560 4.2 1115 468 1.47 3.46 X
130 6 30 10 560 5.3 1988 788.1 1.52 3.58 X
141 8 30 9 580 7.3 3308 1229 1.65 3.88 Y