BaBar silicon vertex tracker: Status and prospects Re, V.; Bondioli, M.; Bruinsma, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2006, Letnik:
569, Številka:
1
Journal Article
B a B ar silicon vertex tracker: Status and prospects Re, V.; Bondioli, M.; Bruinsma, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2006, Letnik:
569, Številka:
1
Journal Article
Recenzirano
The
B
a
B
ar Silicon Vertex Tracker (SVT) has been efficiently operated for six years since the start of data taking in 1999. Due to higher than expected background levels some unforeseen effects ...have appeared. We discuss: a shift in the pedestal for the channels of the AToM readout chips that are most exposed to radiation; an anomalous increase in the bias leakage current for the modules in the outer layers. Estimates of future radiation doses and occupancies are shown together with the extrapolated detector performance and lifetime, in light of the new observations.
Radiation damage studies for the B aB ar Silicon Vertex Tracker Re, V.; Kirkby, D.; Bruinsma, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2005, Letnik:
549, Številka:
1
Journal Article
Recenzirano
The Silicon Vertex Tracker of the
B
aB
ar
experiment is a five-layer, double-sided AC-coupled silicon microstrip detector operating on the PEP-II storage ring at the Stanford Linear Accelerator ...Center. After more than four years of running, the silicon sensors and the front-end electronics in the inner layer have absorbed radiation doses up to 2
Mrad. In this paper we present results from radiation hardness tests and discuss the implications of the absorbed radiation dose on the Silicon Vertex Tracker lifetime.
The Silicon Vertex Tracker (SVT) of the B
aB
ar experiment at the PEP-II asymmetric B factory is a crucial element of the B
aB
ar physics program. The SVT is a five layer device with double-sided ...silicon strip detectors and a custom readout chip based on a time-over-threshold circuit. The SVT is fully operational since the installation in the experiment in 1999. We briefly review the detector performance after more than 3 years of data taking in factory mode. The high-luminosity running of PEP-II through the end of the decade will increase the radiation level in the SVT above its design limit. Radiation issues will be reviewed and results from radiation tests of the various detector components will be presented. We finally discuss the outlook for the long-term running of the SVT.
Radiation hardness and monitoring of the B aB ar vertex tracker Re, V.; Bruinsma, M.; Kirkby, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2004, Letnik:
518, Številka:
1
Journal Article
Recenzirano
The Silicon Vertex Tracker (SVT) is an essential component of the B
aB
ar experiment at the PEP-II asymmetric B factory. The SVT has performed very well and several radiation studies have been ...carried out to determine that it will continue do so up to integrated radiation doses of
5
Mrad
. The SVT radiation monitoring and protection system consists of silicon PIN-diodes, which are suffering from radiation damage, reducing their precision. Diamond sensors are highly resistant to radiation damage and the possibility of replacing the PIN-diodes with diamonds is currently under investigation. Two polycrystalline diamonds have been installed near the B
aB
ar interaction region and show promising results when compared to the PIN-diodes.
The BABAR Silicon Vertex Tracker has been in operation for four years at the PEP-II electron-positron storage ring. During this time the SVT modules have accumulated a radiation dose up to 2 MRad. We ...study the degradation in the performance of the SVT due to this accumulated dose which is highly non uniform across the detector and also within the single crystals. To extrapolate the performance of the detector to the future we study separately the effect of the irradiation on silicon wafers, front end integrated circuits and on a complete detector module under controlled radiation conditions, using a /sup 60/Co source and a 0.9 GeV e- beam. We compare the results to the data from the SVT. In particular we show the dependence of the charge collection efficiency on the radiation dose even when a small stripe of the module is irradiated up to bulk type inversion. Since the modules that lay in the plane of the beams will suffer significant radiation damage, we will describe our plans for their replacement in 2005 and for the operation of the SVT through the lifetime of the BABAR experiment.
Background Although conduct disorder (CD) is associated with an increased susceptibility to substance use disorders, little is known about decision-making processes or reward mechanisms in CD. This ...study investigated decision making under varying motivational conditions in CD. Methods Performances on the Risky Choice Task (RCT) and the Wisconsin Card Sorting Test (WCST) were assessed in 156 adolescents (84 control subjects, 34 with adolescence-onset CD, and 38 with early-onset CD). The RCT was performed twice, once under normal motivational conditions and once under conditions of increased motivation and psychosocial stress. Results Increased motivation and stress led to more cautious decision making and changes in framing effects on the RCT in all groups, although such effects were least pronounced in the early-onset CD group. Participants from both CD subgroups selected the risky choice more frequently than control subjects. Under normal motivational conditions, early-onset CD participants chose the risky choice more frequently in trials occurring after small gains, relative to control subjects and adolescence-onset CD participants. Following adjustment for IQ differences, the groups did not differ significantly in terms of WCST performance. Conclusions Differences in decision making between control subjects and individuals with CD suggest that the balance between sensitivity to reward and punishment is shifted in this disorder, particularly the early-onset form. Our data on modulation of decision making according to previous outcomes suggest altered reward mechanisms in early-onset CD. The WCST data suggest that impairments in global executive function do not underlie altered decision making in CD.
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