Upload
others
View
8
Download
0
Embed Size (px)
Citation preview
Tests of AGATA preamplifiers and hints to improve their performanceTests of AGATA preamplifiers and hints to improve their performance
A. Pullia on behalf of preamplifier team
AGATA Digital Processing workshopAGATA Digital Processing workshop –– Milano,Milano, Italy,Italy, 22 22 -- 2323 SeptemberSeptember 20052005
Outline
• Tests of segment preamps at IKP
• Tests of built-in fast-reset device
• Tests of a digital deoscillator filter
• Tests of a digital baseline controller
• Conclusions
Outline
• Tests of segment preamps at IKP
• Tests of built-in fast-reset device
• Tests of a digital deoscillator filter
• Tests of a digital baseline controller
• Conclusions
AGATA Detector CSP Set ( 12 Segments + 1 Core)
new solid GND concept for the mother board of 12+1 CSPs / Agata_Detector
GND_Layer
Top_Layer
MDR26 connectors
Segment preamplifiers
Segment preamplifiersCore
preamplifier
Tests made with one segmented detector housed in triple cryostat
• 14 – 18 March 2005: GANIL preampssuccesful after damping of a 75 MHz oscillation by increasing the compensation capacitance. Detailed report available upon request.
• 11 – 15 April 2005: MILANO preampssuccesful after damping of a 120 MHz oscillation by reducing bias current of FET and increasing the compensation capacitance. Detailed report available upon request.
FWHM of 122keV-line
0,00
0,20
0,40
0,60
0,80
1,00
1,20
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Segment index
FWHM
[keV
] Reihe1
Reihe2
FWHM of 59.5keV-line
0,00
0,20
0,40
0,60
0,80
1,00
1,20
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
segment index
FWHM
[keV
]
Reihe1
Reihe2
GANIL
Milano
GANIL
Milano
Mean FWHM is 1 keV with GANIL and Milano preamplifiers
Mean FWHM is 0.94 keV with GANIL and Milano
preamplifiers
Comparison of Milano and Ganil preamplifiersMeasurements made by D. Weisshaar
(April 2005)
FWHM of Corewith segments equipped with preamplifiers from
Ganil Milano 122keV: 1.15keV 1.15keV1.3MeV: 2.14keV 2.15keV
Some segment resolutions:Ganil Milano
C2 122keV 0.91keV 0.92keV1.3MeV 1.85keV 1.83keV
C3 122keV 0.90keV 0.90keV1.3MeV 1.81keV 1.81keV
D5 122keV 1.02keV 1.04keV1.3MeV 1.99keV 1.97keV
D6 122keV 1.07keV 1.12keV1.3MeV 1.93keV 1.92keV
Absolute best result
Energy resolution of 1.71/1.77 keV fwhm on 60Co lines (12 April 2005) isone of the best ever obtained withGe detectors !
Outline
• Tests of segment preamps at IKP
• Tests of built-in fast-reset device
• Tests of a digital deoscillator filter
• Tests of a digital baseline controller
• Conclusions
Random arrival of 16.65 MeV events
provided by a poissonian pulser BNC mod. DB-2
The random distribution of negative tails yields a random distribution of reset times, each of
which is smaller than that obtained with no tail
Tests made with MILANO preamplifiers
Negative tails
Inhsignals
Reset time
An accidental AC-coupling in the pulser module causes the output signal to have a zero DC component and so
to assume also negative values
Measurements of the event energy from the reset time
( ) OS EVVkTbTbE +−−+= 2112
21EESS = = photonphoton energyenergy (or (or equivalentequivalent))
T = reset timeT = reset time
bb11, b, b22, k, k11, E, E00 = fitting parameters= fitting parameters
VV11, V, V22 = pre= pre-- and postand post--pulse baselines correction of the tail of the previous events pulse baselines
Francesca Zocca, ”Francesca Zocca, ”A new A new lowlow--noisenoise preamplifierpreamplifier forfor γγ--rayray sensorssensors with smart with smart devicedevice forfor largelarge signal managementsignal management”, ”, Laurea Laurea DegreeDegree ThesisThesis, University of Milano, , University of Milano, OctoberOctober 2004 (in 2004 (in ItalianItalian),), http://http://topserver.mi.infn.ittopserver.mi.infn.it//miesmies//labelet_iiilabelet_iii//download_filedownload_file/capitolo6.doc/capitolo6.doc
Energy resolution in auto-reset mode
Event count rate
Energy resolution @ 16.65 MeV
in HPGe (fwhm)
140 Hz 0.26 %
470 Hz 0.29 %
1.14 kHz 0.30 %
1.44 kHz 0.30 %
2.65 kHz 0.34 %
4.87 kHz 0.44 %
Outline
• Tests of segment preamps at IKP
• Tests of built-in fast-reset device
• Tests of a digital deoscillator filter
• Tests of a digital baseline controller
• Conclusions
A simple approach exists to improve the preamplifier response
PREAMP ADCNUMERICAL
“DEOSCILLATOR” FILTER (FIR)
Insufficient compensation capacitance
The filter goal is to eliminate the ringingswhile preserving the high-frequency content
of the preamplifier output signal
Weights of the numerical “deoscillator”
filter
as obtained from the DECONVOLUTION between the oscillating signal of the preamplifier and the wanted
ideal response
Example: deoscillator filter removes ringings from a disturbed pulse shape
Outline
• Tests of segment preamps at IKP
• Tests of built-in fast-reset device
• Tests of a digital deoscillator filter
• Tests of a digital baseline controller
• Conclusions
Tests of a digital BL controller
in
out
out - in
in
out
ADC input
200 mV /
1 µs /
0.5 V /
0.5 ms /
in outADC input
12 bit 100 MHz
14 bit 100 MHz
In XILINX Spartan 3
A. Pullia, S. Riboldi, G.M. Franchi, F. ZoccaActive control of the baseline of digitized preamplifiers with sliding-scale correction2004 IEEE Nucl. Sci. Symp. Conference Record, Rome, ITALY, 16-22 Oct. 2004
The baseline can now walk across the preamplifier full range without causing ADC saturation !
Analysis of observed signals
Noise of output signal is 0.85 mV (1.75 LSB) r.m.s.
For slow input signals an amplitude-folding effect occurs, which yields an extended input dynamic range…
...which in turn yields an extended range on the individual signals
The extended range (bit gain) increases as the input signal gets
slower
Conclusion
• Full sets of Ganil and Milano segment preamplifiers have been installed in triple cryostat and operated succesfully in conjunction with one segmented detector
• All preamplifiers are equipped with over-threshold fast-reset device. Energy measurements are still possible in reset mode (up to 50 MeV) and energy resolution is good (0.26 to 0.44% @ 17 MeV)
• Techniques to improve integrity and reduce randomwalks of preamplifier signals are available