CN202216921U

CN202216921U - Digital positron annihilation life spectrometer device

Info

Publication number: CN202216921U
Application number: CN2011202928863U
Authority: CN
Inventors: 成斌; 叶邦角
Original assignee: University of Science and Technology of China USTC
Current assignee: University of Science and Technology of China USTC
Priority date: 2011-08-12
Filing date: 2011-08-12
Publication date: 2012-05-09
Anticipated expiration: 2021-08-12

Abstract

The utility model relates to a digital positron annihilation life spectrometer device which is composed of a first photomultiplier tube (1), a second photomultiplier tube (11), a first high voltage power supplier (2), a second high voltage power supplier (12), a first flashing body (3), a second flashing body (13), a clamping source for material to be tested (4), a high-speed analog-to-digital conversion circuit main board (5), a high-speed analog-to-digital conversion circuit secondary board (6), a bridge circuit (7) and a computer (8). According to the digital positron annihilation life spectrometer device, the structure of the positron annihilation life spectrometer is greatly simplified, the reliability of the instruments is improved, and the construction cost is reduced; and meanwhile, the spectrometer has the advantages of low noise, long-time stable performance, small environment temperature influence, flexible online or offline data processing, automatic search of an optimal energy window, and the like.

Description

A kind of digitizing positron annihilation life spectrometer device

Technical field

The utility model belongs to the applied nuclear technologies field, is specifically related to a kind of digitizing positron annihilation life spectrometer device.

Background technology

Conventional positron life spectrometer is by scintillator probe, high voltage supply device, constant proportion timing discrminator, fast coincidence circuit, time-delay case, time-amplitude analyzer, NIM cabinet, microcomputer multichannel card; Computing machine is formed; Wherein constant proportion timing discrminator, fast coincidence circuit, time-amplitude analyzer belong to the plug-in unit of NIM cabinet, and the microcomputer multichannel card is inserted in the PCI slot of computing machine.The scintillator probe detection is behind gamma-rays; Get into CFD from negative signal of probe anode output; Accomplish two parts work by CFD; A part of work is carried out amplitude discriminator to input signal, when input signal amplitude meets up and down threshold range, export one by the definite standard SCA signal of constant proportion timing method.Next in CFD, be divided into two-way SCA output signal: one tunnel output positive signal is used for meeting soon to trigger enabling signal, and another road output negative signal gets into TAC after time delay.When meeting the out gate signal soon to behind the TAC; The TAC of two-way SCA signal will convert the signal that is directly proportional with amplitude the mistiming to; Range signal is converted into numerical value is stored at last in the computer storage hardware thereby carry out amplitude discriminator by MCA, it is the positron life spectrum that some such incidents are accumulated resulting composing.

Conventional positron annihilation life spectrometer needs more NIM plug-in unit; Setting up debugging needs long time, as long as one of them plug-in unit goes wrong, a whole set of spectrometer cannot normally use; The maintenance of spectrometer need be especially careful, and the expense of setting up a cover spectrometer simultaneously is also higher.When spectrometer was worked, the NIM plug-in unit was acted upon by temperature changes bigger, need be operated under the constant temperature.Because Data Acquisition belongs to online treatment, system's dead time of this kind mode is less, but when a part of data in the measurement go wrong, must from the beginning remeasure, and its processing method of data is also confirmed by hardware is unique.

The utility model content

The purpose of the utility model is for the establishment that makes spectrometer simply saves time, and the reduction construction cost is easy to maintenance, reduces to receive the influence of environment temperature, has data processing method more flexibly.

The technical solution that the utility model is taked is following:

A kind of digitizing positron annihilation life spectrometer device is made up of first photomultiplier 1, second photomultiplier 11, the first high voltage supply device 2, the second high voltage supply device 12, primary scintillator 3, secondary fluor 13, test substance folder source 4, high-speed A/D conversion circuit mainboard 5, high-speed A/D conversion circuit slave plate 6, bridgt circuit 7, computing machine 8;

The first high voltage supply device 2, the second high voltage supply device 12 connect with first photomultiplier, 1, the second photomultiplier 11 respectively;

Primary scintillator 3, secondary fluor 13 through transmissivity greater than 95%, refractive index greater than 1.3 optics silicone oil respectively with

first photomultiplier

1,11 couplings of second photomultiplier, with the aluminum hull encapsulation, guarantee the light leakproofness again;

The output signal of first photomultiplier 1 is connected to the input end of analog signal of high-speed A/D conversion circuit mainboard 5 through concentric cable;

The output signal of second photomultiplier 11 is connected to the input end of analog signal of high-speed A/D conversion circuit slave plate 6 through concentric cable;

High-speed A/D conversion circuit mainboard 5 is connected through bridgt circuit 7 with high-speed A/D conversion circuit slave plate 6;

High-speed A/D conversion circuit mainboard 5 is connected with computing machine 8 through pci bus interface with high-speed A/D conversion circuit slave plate 6.

The good effect of the utility model is:

The positron annihilation life spectrometer of the routine that compares; We have simplified the spectrometer structure by the digitizing positron annihilation life spectrometer of development greatly; Do not re-use corresponding N IM plug-in unit; Replace with the high-speed figure capture card, setting up of spectrometer become with debugging simply save time, greatly strengthened the reliability of instrument.Reduced the construction cost of spectrometer, spectrometer is promoted in application market more easily.Simultaneously, this cover digitizing positron annihilation life spectrometer also has low noise, and long-time stable performance receives the temperature effect of environment less, and online flexibly or off-line data is handled, and can obtain more physical message as required.Can realize the storage of raw data very easily, carry out off-line data and handle, improve the service efficiency of spectrometer.Utilize digitized characteristics, the method that no longer needs manually to survey power spectrum is regulated Canon window.And make into as required, seek optimized ability window automatically through the life spectrum of measurement standard sample after the appointment relevant parameter, further improve the performance and the efficient of instrument.

Description of drawings

Fig. 1 is the utility model structural drawing.

Embodiment

Below in conjunction with Figure of description the utility model is further specified.

At first use the identical object under test of two thickness with the positron emission source ²²Na is clipped in the middle, and object under test thickness generally requires greater than 1mm, ²²Na source radioactivity is greatly about tens microcurie magnitudes.The gamma-ray photon detector that is made up of

photomultiplier

1,11 and

BaF2 scintillator

3,13 is placed in test substance folder 4 both sides, source, survey respectively by ²²The Na radioactive source sends gamma-ray photon that energy that positron decay produces is 1.28MeV and positron, and in object under test, to fall into oblivion the energy that produces be the gamma-ray photon of 511keV, i.e. the start signal of positron annihilation and termination signal.Wherein, BaF2 scintillator volume is φ 30 * 15mm, and greater than 95%, refractive index is coupled greater than 1.3 optics silicone oil and photomultiplier, guarantees the light leakproofness with the aluminum hull encapsulation again through transmissivity.When the BaF2 scintillator receives gamma-ray photon, can change into the receivable fluorescent photon of photomultiplier to gamma-ray photon, the time level of photomultiplier at first is converted into a spot of electronics with it after receiving fluorescent photon.The high

voltage supply device

2,12 that is connected with

photomultiplier

1,11 can be taken between the level each dozen of photomultiplier and form electric field; Under this effect of electric field; Time,, the little electrons sent of level was accelerated multiplication; Final produce an amplitude, by the anode of photomultiplier or beat and take level to export the energy positive correlation of its amplitude and gamma-ray photon greatly about the electric impulse signal of several V.Wherein, the high pressure of high

voltage supply device

2,12 is greatly about several kilovolts, and rated current is at several mA.

The electric signal that is produced by photomultiplier transmits through concentric cable, can effectively avoid the space electromagnetic interference (EMI).The signal of two photomultipliers is transferred to high-speed A/D conversion circuit ADC mainboard 5 and high-speed A/D conversion circuit slave plate 6 respectively, by analog to digital conversion circuit simulating signal is carried out high-speed sampling, is converted into digital signal and is stored in plate and carry in the buffer memory.High-speed ADC mainboard 5 is connected through bridgt circuit 7 with high-speed ADC slave plate 6, guarantees the clock synchronization of high-speed ADC mainboard 5 and high-speed ADC slave plate 6, reduces the time measurement error.High-speed ADC satisfies sampling rate greater than 2GS/s here, and bandwidth is greater than 1GHz.High-speed ADC mainboard 5 all passes through pci interface with high-speed ADC slave plate 6 and links to each other with computing machine.Write when full when plate carries buffer memory, by programmed control plate is carried and data cachedly write calculator memory or hard disk, and empty plate and carry buffer memory and work on.

After obtaining digital signal, can select online signal Processing as required perhaps with carrying out processed offline behind the data-storing.No matter online treatment or processed offline all are to use self-compiling program that the signal waveform that obtains is handled automatically.At first screen and declare choosing, promptly to being start signal, termination signal or noise according to judgement received signals such as amplitude areas behind the waveform fitting.The selected appropriate threshold of Automatic Program will be declared the real event example signal of selecting and carry out digital constant proportion regularly after judging.Soon the certain proportion value of the amplitude of match afterpulse waveform is as standard, and like 20% of range value, pulse front edge promptly is decided to be the zero-time of this pulse in the position at this standard value place.This kind timing method can effectively reduce the amplitude autokinetic effect to time-resolved influence.

When a large amount of examples of accumulation, the mistiming of calculating start signal and termination signal, make after the statistical Butut, just can obtain the annihilation life spectrum of positron in test substance.

Claims

1. digitizing positron annihilation life spectrometer device is characterized in that: affiliated digitizing positron annihilation life spectrometer device is made up of first photomultiplier (1), second photomultiplier (11), the first high voltage supply device (2), the second high voltage supply device (12), primary scintillator (3), secondary fluor (13), test substance folder source (4), high-speed A/D conversion circuit mainboard (5), high-speed A/D conversion circuit slave plate (6), bridgt circuit (7), computing machine (8);

The first high voltage supply device (2), the second high voltage supply device (12) are connected with first photomultiplier (1), second photomultiplier (11) respectively;

Primary scintillator (3), secondary fluor (13) through transmissivity greater than 95%, refractive index greater than 1.3 optics silicone oil respectively with first photomultiplier (1), second photomultiplier (11) coupling, with the aluminum hull encapsulation, guarantee the light leakproofness again;

The output signal of first photomultiplier (1) is connected to the input end of analog signal of high-speed A/D conversion circuit mainboard (5) through concentric cable;

The output signal of second photomultiplier (11) is connected to the input end of analog signal of high-speed A/D conversion circuit slave plate (6) through concentric cable;

High-speed A/D conversion circuit mainboard (5) is connected through bridgt circuit (7) with high-speed A/D conversion circuit slave plate (6);

High-speed A/D conversion circuit mainboard (5) is connected with computing machine (8) through pci bus interface with high-speed A/D conversion circuit slave plate (6).