Evaluation of FOXFET biased ac-coupled silicon strip detector prototypes for CDF SVX upgrade

Silicon microstrip detectors for high-precision charged particle position measurements have been used in nuclear and particle physics for years. The detectors have evolved from simple surface barrier strip detectors with metal strips to highly complicated double-sided AC-coupled junction detectors. The feature of AC-coupling the readout electrodes from the diode strips necessitates the manufacture of a separate biasing structure for the strips, which comprises a common bias line together with a means for preventing the signal from one strip from spreading to its neighbors through the bias line. The obvious solution to this is to bias the strips through individual high value resistors. These resistors can be integrated on the detector wafer by depositing a layer of resistive polycrystalline silicon and patterning it to form the individual resistors. To circumvent the extra processing step required for polysilicon resistor processing and the rather difficult tuning of the process to obtain uniform and high enough resistance values throughout the large detector area, alternative methods for strip biasing have been devised. These include the usage of electron accumulation layer resistance for N{sup +}{minus} strips or the usage of the phenomenon known as the punch-through effect for P{sup +}{minus} strips. In this paper we present measurement results about the operation and radiation resistance of detectors with a punch-through effect based biasing structure known as a Field OXide Field-Effect Transistor (FOXFET), and present a model describing the FOXFET behavior. The studied detectors were prototypes for detectors to be used in the CDF silicon vertex detector upgrade

Quintessence cosmology and the cosmic coincidence

Within present constraints on the observed smooth energy and its equation of state parameter w_Q=P/#rho#_Q, it is important to find out whether the smooth energy is static (cosmological constant) or dynamic (quintessence). The most dynamical quintessence fields observationally allowed are now still fast-rolling and no longer satisfy the tracker approximation if the equation of state parameter varies moderately with cosmic scale a. We are optimistic about distinguishing between a cosmological constant and appreciably dynamic quintessence, by measuring average values for the effective equation of state parameter w_Q(a). However, reconstructing the quintessence potential from observations of any scale dependence w_Q(a) appears problematic in the near future. For our flat universe, at present dominated by smooth energy in the form of either a cosmological constant (LCDM) or quintessence (QCDM), we calculate the asymptotic collapsed mass fraction to be maximal at the observed smooth energy/matter ratio R_0#propor to#2. Identifying this collapsed fraction as a conditional probability for habitable galaxies, we infer that the prior distribution is flat in R_0 or #OMEGA#_m_0. Interpreting this prior as a distribution over theories, rather than as a distribution over unobservable subuniverses, leads us to heuristic predictions about the class of future quantum cosmology theories and the static or quasi-static nature of the smooth energy. (orig.)Available from TIB Hannover: RA 2999(01-147) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman