经典外文翻译底土的土壤结构和饱和导水率毕业论文设计文档格式.docx

1、Low-cost programmable pulse generator for particle telescope calibrationAbstractIn this paper we present a new calibration system for particle telescopes including multi pulse generator and digital controller. The calibration system generates synchronized pulses of variable height for every detector

2、 channel on the telescope. The control system is based on a commercial microcontroller linked to a personal computer through an RS-232 bidirectional line. The aim of the device is to perform laboratory calibration of multi-detector telescopes prior to calibration at accelerator. This task includes e

3、valuation of linearity and resolution of each detector channel, as well as coincidence logic. The heights of the pulses sent to the detectors are obtained by Monte Carlo simulation of telescope response to a particle flux of any desired geometry and composition. Elsevier Science B.V. All rights rese

4、rved.To assure a correct interpretation of data obtained with scientific instruments onboard satellites, as well as to compare these data with those of similar instruments, a thorough pre-flight calibration is required. For solar and cosmic ray particle telescopes, this calibration is usually carrie

5、d out in two steps: first, a calibration of each individual detector using radioactive sources and standard nuclear instrumentation （NIM or CAMAC modules）,following by a final test of the whole telescope performed in a particle accelerator site. The success of calibration on accelerator requires tha

6、t, prior to the experiences, all detectors and electronics parameter （polarization voltages, amplifier gains and shaping times, thresholds, etc.） have nearly definitive values. Here we propose a cheap and simple pre-calibration procedure based on a new system that we have called Programmable Pulse G

7、enerator （PPG）. The PPG developed in our laboratory has been designed for a specific instrument, a four-detector cosmic ray telescope, but it can easily be modified for similar experiments.The standard calibration procedure for individual detectors and their electronic chains consists of introducing

8、 pulses of known amplitudes coming from a pulse generator, together with the pulses released in the detector by particles coming from a radioactive source. However, these standard pulse generators do present several limitations: The pulse amplitude must be set manually. Thus, to generate the pulses

9、that different particles with different energies would release on the detectors, it is necessary to change the pulse heights every time.Standard pulse generators only provide one output signal, so either several modules are needed to calibrate a complete telescope, or it is necessary to split the si

10、ngle output in order to get several signals. It is difficult to check the coincidence logic because the four signals are not independent.To overcome these difficulties, pulse generators of programmable amplitude and rate have been proposed. Abdel-Aal 1presented a programmable random pulse generator

11、where the height and separation of individual pulses are controlled by software.But in his scheme the pulses are released directly from a digital-to-analog converter（DAC）,thus having the temporal characteristics of the DAC output. Our purpose is to generate variable height analog pulses with similar

12、 shape to that released by nuclear detectors.The low-cost PPG presented here is intended to introduce every detector channel ，the pulses released by any particle flux supposed to be encountered by the instrument on real experiments （in our case, on outer space environment）. The proposed pre-calibrat

13、ion scheme is sketched in the diagram of Fig 1. For a big number of simulated events, the energy signals released at the different detectors of the telescope are stored on a personal computer （PC）. For each individual event, the energy signal data are sent through a bidirectional RS-232-C line to th

14、e PPG, which transforms the results of the simulation into real pulses and sends them to the real instrument.Fig 1 2 PPG descriptionThe design of the PPG is divided into two functional modules: digital electronics and analog electronics, whose block diagrams are enclosed in dashed boxes shown in Fig

15、2. The data arriving at the digital module from the PC are sent to 12 bit DAC. The DAC output voltages are transformed in the analog module into suitable pulses, ready to be introduced into the test input of the related detector channel of the telescope.Analog and digital modules are described with

16、some detail in Sections 2.1 and 2.2. In Section 2.3 we describe some noise problems related with the microcontroller, and the way we found to solve them.2.1 Analog moduleThis module must be capable of producing signal pulses similar to those generated in the detectors by the passage of energetic charged particles, whose shape can be described by the following function: （1）The relevant signal parameters are the pulse height o