Summary of the invention
The purpose of the present invention is to provide a kind of non-contact object surface charge photomultiplier transit image intensifers.
The technical scheme is that a kind of non-contact object surface charge photomultiplier tube amplifier, by charge detection
Photocathode, light input system, dynode, anode, power-supply system, electron multiplication system signal output end are constituted;One kind is non-to be connect
The front end for touching body surface charge photomultiplier tube amplifier is charge detection photocathode, charge detection photocathode front end face
Sectional area S, testee surface charge density are ne/ Δ S, and Δ S is tested area, and ne is the quantity of electric charge on Δ S, meet S > Δ
Between S, S=Δ S*105%-120%, 0.001~1mm of distance of reaction;Charge detection photocathode rear end face is arc, constant light
The constant intensity light beam of input system is that the curved surfaces central area is irradiated to through glass window, and light irradiates cathode and generates light
Electrical effect emits primary electron, and dynode D is made of photoemissive material metal, and electronics is from photocathode to each dynode
D1, D2... Dn, the positive integer of n≤6, then on anode, power-supply system voltage added by D1, D2... Dn is incremental according to this
, the electronics generated on each photocathode accelerates under electric field action, focuses through cambered surface, successively bombards D1, D2...
Dn generates more electronics, reaches anode after 6 or more dynodes, the photoelectron through doubling by anode collect and
Output light electric current generates signal voltage A in load, constitutes electron multiplication system signal output end.
It is vacuumized inside non-contact object surface charge photomultiplier tube, charge detection photocathode integrally uses made of metal
At charge detection photocathode rear end face uses photoemission metal material plated film.
The light beam of constant light input system is constant intensity light beam during operation, and light source frequency is fixed frequency, can root
Intensity of illumination is adjusted according to detection charge density.
Electron multiplication system signal output end is provided with filter.
Working principle: when incident intensity increases, according to photon it is assumed that the intensity of incident light (is led to i.e. in the unit time
Cross the luminous energy of specific vertical area) it is decided by pass through the number of photons of specific vertical area in the unit time, pass through in the unit time
The number of photons of metal surface also just increases, and then, photon also increases with the electron collision number in metal, thus in the unit time
The photoelectron escaped from metal surface also increases, and electric current also increases with it;Equally, if incident intensity is constant, metal
Surface charge increases, so that photon also increases with the electron collision number in metal, thus escapes in the unit time from metal surface
Photoelectron out also increases, and electric current also increases with it.The energy for the electrons absorption photon being irradiated to by light beam, but wherein machine
System in accordance be it is a kind of it is non-have entirely i.e. completely without criterion, all energy of photon must all be absorbed, for overcoming work function, otherwise
This energy can be released.If the energy that electron institute absorbs can overcome work function, and also dump energy, then this residual energy
Amount can become kinetic energy of the electronics after being launched.
Work function W is least energy required for launching a photoelectron from metal surface.If being transformed into frequency
From the point of view of angle, the frequency of photon has to be larger than the limiting frequency of metallicity, can just give the enough energy of electronics and overcome evolution
Function.Relationship between work function and limiting frequency v0 are as follows: W=h*v0, wherein h is Planck's constant, be light frequency be h*v0
The energy of photon.After overcoming work function, photoelectronic maximum kinetic energy KmaxFor Kmax=hv-W=h(v-v0) wherein, hv is optical frequency
Rate is had by the photon of v and by the energy of Electron absorption.
Actual requirement kinetic energy must be positive value, and therefore, light frequency has to be larger than or be equal to limiting frequency, photoelectric effect ability
Occur.To avoid generating excessive photoelectric current, actual charge signal is covered, the frequency of light used in the present invention is slightly larger than pole
The illumination of frequency limit rate, light reduces as far as possible, needs to carry out repeatedly intensity of the comparative experiments to determine illumination, so that photoelectric effect
The density of testee surface charge can be characterized.
The present invention is using multiplication polar form photomultiplier tube: multiplication polar form photomultiplier tube is by photocathode, multiplier stage and anode
Deng composition, by glass-encapsulated, internal high vacuum, multiplier stage is made of a series of dynodes again, and each dynode work is preceding
Under the higher voltage of grade.Photon strikes photocathode material generates photoelectron after overcoming the work function of photocathode, through electric field acceleration
After focusing, with higher energy impact first order multiplier tube, emit the electronics of more low energy, these electronics are successively added
Fast multiplication by stages pole downwards is hit, and a series of geometry multiplication by stages is caused, and last electronics reaches anode, and charge adds up to be formed sharp
Current impulse can characterize the photon of input.
During the test, charge detection photocathode (4) is made of metal, when charge detection photocathode (4) are close to tested
When object (1) surface, there are test charge (2), charge detection photocathode (4) front ends can generate charge inducing on testee surface
It (3), is positive charge, charge inducing produced by charge detection photocathode (4) rear end is negative electrical charge, and light input system (5) light shines
It is mapped to charge detection photocathode (4) rear end face, generates external photoeffect, photocathode excites photoelectrons into vacuum.These light
Electronics enters dynode system by focusing electrode electric field, and is amplified by the multiplication that further Secondary Emission obtains.Then amplification
Electronics afterwards is used anode to collect and is exported as signal.Due to it using secondary make evolution photo-multiplier, obtain
Much higher than the sensitivity of photoelectric tube, it is capable of measuring faint optical signal.Photomultiplier tube includes cathode chamber and by several dynodes (6)
Secondary Emission dynode system two parts of composition (see figure).The structure of cathode chamber is related with the size and shape of photocathode K, it
Effect is the electron focusing first dynode D1 minimum in area ratio time that cathode is generated by external photoeffect under light illumination
Surface on.Secondary Emission dynode system is most complicated part.Dynode mainly can be in smaller incident electron energy by those
Under there is the material of higher sensitivity and secondary emissionratio to be made.Common dynode material has the silver-colored magnesium of antimony caesium, oxidation
Alloy and the copper beryllium alloy of oxidation etc..The shape of dynode, which should have, to be conducive to the electronics that previous stage emits being collected into next pole.?
Successively added with the positive voltage gradually increased in each dynode (6) D1, D2, D3 ... and anode A, and the voltage between two neighboring pole
Difference should make secondary emissionratio be greater than 1.In this way, the electronics of photocathode transmitting is under the action of D1 electric field with high fast direction dynode
D1 generates more secondary emission electrons, and then these electronics fly under the action of D2 electric field to D2 again.Under so continuing
It goes, the secondary emission electron that excitation is multiplied by each photoelectron is finally collected by anode.These impact the electronics energy of time pole
Time pole is set to discharge more electronics, they are focused on second of pole again.In this way, generally doubled more than ten times, times magnification
Number can reach 108~1010.Finally, the anode in high potential is collected into the photoelectric current being exaggerated.Export electric current and incident light subnumber
It is directly proportional.The whole process time about 10-8Second.There are two disadvantages for photomultiplier tube: when 1. sensitivity is because of strong illumination or because of irradiation
Between it is too long and reduce, partly restore again after stopping irradiation, this phenomenon is known as " tired ";2. time pole surface each point sensitivity
Unevenly.
Operation characteristic
1. stability
The stability of photomultiplier tube is determined by many factors such as device self character, working condition and environmental conditions.Pipe
It is many that son exports unstable situation during the work time, mainly has:
A. it manages and is jumped caused by bad interior electrode welding, connection loosing, the poor contact of cathode elastic slice, interpolar point discharge, arcing etc.
Jump property shakiness phenomenon, signal are suddenly big or suddenly small.
B. the wild effect of the continuity of the anode output too big generation of electric current and fatigability.
C. influence of the environmental condition to stability.Environment temperature increases, tube sensitivity decline.
D. wet environment causes to leak electricity between pin, causes dark current increase and shakiness.
E. ambient electromagnetic field interference causes work unstable.
2. maximal work voltage limit operating voltage refers to the upper voltage limit that pipe allows to apply.Higher than this voltage, pipe
Son generates electric discharge and even punctures.
Beneficial effect
Photomultiplier transit of the present invention is established in external photoeffect, secondary and electron-optical theoretical basis, and height is combined
The features such as gain, low noise, high-frequency response and big signal reception area are a kind of with high sensitivity and ultrafast time response
Photosensitive electron tube, can work in ultraviolet, visible and near infrared region spectral regions.With noise, low (dark current is less than
1nA), the features such as response is fast, receiving area is big has good development potentiality.
Embodiment 1: the technical scheme is that including by charge detection photocathode 4, light input system 5, dynode
6, anode 7, power-supply system 8, electron multiplication system signal output end 9 are constituted;A kind of non-contact object surface charge photomultiplier transit
The front end of pipe amplifier is charge detection photocathode 4,4 front end face sectional area S of charge detection photocathode, 1 table of testee
The density of surface charge is ne/ Δ S, and Δ S is tested area, and ne is the quantity of electric charge on Δ S, meets S > Δ S, S=Δ S*105%-120%,
Between 0.001~1mm of distance of reaction;4 rear end face of charge detection photocathode is arc, constant light input system 5 it is constant strong
Degree light beam is that the curved surfaces central area is irradiated to through glass window, and light irradiates cathode and generates the primary electricity of photoelectric effect transmitting
Son, dynode 6D are made of photoemissive material metal, from photocathode K to each dynode D1, D2... again to anode 7
On, voltage added by power-supply system 8 is each electronics incremental according to this, generate on photocathode K, is added under electric field action
Speed is focused through cambered surface, is bombarded second dynode D2, is generated more secondary electrons ..., by 6 or more dynodes
After reach the last one dynode, i.e. anode 7, the photoelectron through doubling is collected and output light electric current by anode 7, is produced in load
Raw signal voltage A, constitutes electron multiplication system signal output end 9.
It is vacuumized inside non-contact object surface charge photomultiplier tube, charge detection photocathode 4 is whole to use metal
It is made, 4 rear end face of charge detection photocathode uses photoemission metal material plated film.
The light beam of constant light input system 5 is constant intensity light beam during operation, and light source frequency is fixed frequency, can root
Intensity of illumination is adjusted according to detection charge density;Electron multiplication system signal output end 9 is provided with filter.
Since gain of photomultiplier height and response time are short, and due to its output electric current and incident photon and cathode table
Face electron number is directly proportional, its advantage is that: measurement accuracy is high, can measure the quick variation of charge.Cerium-antimonide photocathode can be selected
Multiplier tube, such as RCA1P21.The very big quantum efficiency of this photomultiplier tube is 20% or so near 4200 angstroms.There are also one kind
The photomultiplier tube of double alkali photocathodes, such as GDB-53.The numerical value of its signal-to-noise ratio is order of magnitude greater compared with RCA1P21, and undercurrent is very
It is low.
Common photomultiplier tube can only once measure an information, i.e. port number is 1.Since port number is thin by anode end
A channels up to a hundred are only accomplished in the limitation of wire, but this is sufficient for the detection of faint charge variation.
The present invention has been described in detail through specific embodiments, but these are not constituted to limit of the invention
System.Without departing from the principles of the present invention, those skilled in the art can also make many modification and improvement, these are also answered
It is considered as protection scope of the present invention.