G. Boella

ENERGY LOSS FOR ELECTRONS IN THE HELIOSPHERE AND LOCAL INTERSTELLAR SPECTRUM FOR SOLAR MODULATION

Galactic Cosmic Rays (GCR) entering the Heliosphere are affected by the solar modulation, which is a combination of diffusion, convection, magnetic drift, and adiabatic energy losses usually seen as a decrease of the flux at low energies (less than 10 GeV). We improved a quasi time-dependent 2D Stochastic Simulation code describing such effects. We focused our attention on the electron modulation, adding energy losses mechanisms in the Heliosphere that can be neglected for protons and ions: inverse Compton, ionization, synchrotron, and bremsstrahlung. These effects have been evaluated in the region affected by the solar magnetic field, up to 100 AU, where the environment conditions are not constant, especially the magnetic field intensity, and the photon density. In our calculation the inverse compton energy losses are dominant, but they contribute only a few percent in comparison with the adiabatic losses. We also compared the Local Interstellar Spectrum (LIS) of primary electrons with experimental data collected in the past years at energies 20 GeV. We found that, inside one standard deviation, LIS fits the data and can be used in a Monte carlo code reproducing CR propagation in the Heliosphere.

Latitudinal Dependence of Cosmic Rays Modulation at 1 AU and Interplanetary-Magnetic-Field Polar Correction

The cosmic rays differential intensity inside the heliosphere, for energy below 30u2009GeV/nuc, depends on solar activity and interplanetary magnetic field polarity. This variation, termed solar modulation, is described using a 2D (radius and colatitude) Monte Carlo approach for solving the Parker transport equation that includes diffusion, convection, magnetic drift, and adiabatic energy loss. Since the whole transport is strongly related to the interplanetary magnetic field (IMF) structure, a better understanding of his description is needed in order to reproduce the cosmic rays intensity at the Earth, as well as outside the ecliptic plane. In this work an interplanetary magnetic field model including the standard description on ecliptic region and a polar correction is presented. This treatment of the IMF, implemented in the HelMod Monte Carlo code (version 2.0), was used to determine the effects on the differential intensity of Proton at 1 AU and allowed one to investigate how latitudinal gradients of proton intensities, observed in the inner heliosphere with the Ulysses spacecraft during 1995, can be affected by the modification of the IMF in the polar regions.

Dynamic and low-frequency noise characterization of Si-Ge heterojunction-bipolar transistors at cryogenic temperatures

We present the characterization of the static and low-frequency noise performances of some commercial Si-Ge heterojunction bipolar transistors from 4.2 K to room temperature. The low injection region of operation was considered in view of their possible applications for the readout of array of cryogenic detectors.

AMS-02 photon data reduction approach

G. Boella, M.J. Boschini, C. Consolandi, S. Della Torre, M. Gervasi, D. Grandi, E. Memola, S. Pensotti, P.G. Rancoita, and M. Tacconi Istituto Nazionale di Fisica Nucleare, INFN Milano-Bicocca, Milano (Italy) Department of Physics, University of Milano Bicocca, Milano (Italy) Department of Physics, University of Insubria, Como (Italy) 4 CILEA, Segrate (MI) (Italy) E-mail: cristina.consolandi@mib.infn.it E-mail: elisabetta.memola@mib.infn.it

The noise behavior of silicon JFET transistors from room temperature down to 80K

We have designed and built a very simple and efficient instrument that allows performing very accurate noise measurements of transistors at any biasing conditions, from room temperature down to cryogenic temperatures. This way a study has been possible of the noise behavior of Silicon JFETs for both the low frequency and the high frequency white noise. We explored a wide range of biasing conditions, starting from a power dissipation of only 2 μW up to 1 μW. Concerning white noise, evidence was found for the hot electron effect: it was negligible at small power dissipation and evident at large power. An experimental study was made of the low frequency noise. Its interpretation was developed based on the Generation Recombination theory. Many JFET samples were investigated, made with different technologies and having different gate area.

Dynamic and low frequency noise characterization at cryogenic temperatures of Si-Ge heterojunction-bipolar transistors

We present the characterization of the static and noise performances of some commercial Si-Ge heterojunction bipolar transistors from 4.2 K to room temperature. The region of operation considered was the low injection one in view of their possible applications for the readout of an array of cryogenic detectors.

Fully integrated readout channel with amplitude and time measurement for AMS experiment on ISSA

AMS (Anti-Matter Spectrometer) is a high energy physics experiment to be installed on the International Space Station Alpha (ISSA). The goal of this experiment is to search for antimatter in space. In one section of this experiment an array of sensors is used to detect incoming particle trajectory. Each of these sensors, when it is hit by a particle, gives a charge pulse Qin, which is the input signal for one readout channel. The purpose of each readout channel is to collect the signal charge and to produce two voltage levels: one must be proportional to the amount of charge Q while the other is required to be proportional to the delay, with respect to the hit time, of a fixed instant To, common to all the channels in the system. The maximum charge amount which can be injected into the channel is 6 pC; for the amplitude measurement an 8 bit resolution is required. On the other hand, for the time measurement a 3 ns precision is required, with a 6 bit accuracy output signal. Due to the large number of these readout channels and to the reduced energy available in the space station, a low power consumption for each channel is allowed (<5.5 mW). The whole readout system has been designed in HF3CMOS, a BiCMOS technology with 1.2 /spl mu/m minimum CMOS channel length. The system operates with a single 4 V supply consuming 4.8 mW.

A low power dissipation front-end readout for space instrumentation

We present a first prototype realized for the readout of a straw tube for space application, made in a monolithic Bi-CMOS process. The circuit system consists of a charge sensitive preamplifier followed by an RC-CR shaping filter of 20 nsec peaking time. The charge preamplifier, which has an NPN bipolax input transistor, is able to feature about 2000 el RMS of Equivalent Noise Charge with a power dissipation of about 3.5 mW. The shaping filter circuit proposed and prototyped is well working and has shown to fulfill the required specifications.

A readout channel with 1 nF fully integrated capacitor for AMS space experiment

A complete read-out channel to be used in the trigger section of the AMS experiment on the space station is proposed. The channel is composed by a CSP and a RC-CR shaper. From a single 5 V supply voltage the complete channel power consumption is between 9 mW and 19 mW with input MOS device current level between 1 mA and 3 mA. The shaper implements a 1 /spl mu/s shaping time: this has been realized with two fully-integrated capacitors of 0.5 nF. The experimental results demonstrate the validity of the approach.