CN100546452C - A kind of magnetic shielding device that is used for the multi-layer compound structure of shielding strong magnetic field - Google Patents
A kind of magnetic shielding device that is used for the multi-layer compound structure of shielding strong magnetic field Download PDFInfo
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- CN100546452C CN100546452C CNB2006101138245A CN200610113824A CN100546452C CN 100546452 C CN100546452 C CN 100546452C CN B2006101138245 A CNB2006101138245 A CN B2006101138245A CN 200610113824 A CN200610113824 A CN 200610113824A CN 100546452 C CN100546452 C CN 100546452C
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Abstract
The present invention relates to nuclear electronics and nuclear detection technology field, a kind of magnetic shielding device that is used for the multi-layer compound structure of shielding strong magnetic field is disclosed, at at present general photomultiplier magnetic screen design can't shielding strong magnetic field problem, adopt multi-layer compound structure, comprise three layers from outside to inside: the silicon steel parts are the intermediate layer; Alloy component is an internal layer; Solenoid coil is outer; Solenoid coil produces the magnetic field opposite with external magnetic-field direction, and high-intensity magnetic field is weakened significantly; The silicon steel parts have higher magnetic field saturation, and external magnetic field further is reduced to several Gauss, and innermost layer is an alloy component, have very high low-intensity magnetic field permeability, remaining magnetic field further are reduced to below the 0.001Gauss, far below the earth magnetic field level.The present invention can make conductively-closed photomultiplier operate as normal under high-intensity magnetic field, has a wide range of applications at nuclear electronics and nuclear detection technology field.
Description
Technical field
The present invention relates to nuclear electronics and nuclear detection technology field, particularly a kind of photomultiplier magnetic shielding device that is used for shielding strong magnetic field.
Background technology
Photomultiplier is a kind of photoelectric detector based on photoelectric effect, secondary, weak one can be converted to measurable signal of telecommunication, have the detectivity height, time response is fast, multiplication factor is big, photoelectric characteristic good linearity, stable performance, advantage such as easy to use, is widely used in fields such as spectroscopy, nuclear physics, medical science.Photomultiplier mainly is made up of photo-emissive cathode (photocathode) and focusing electrode, dynode (dynode) and electron collector (anode) etc., and all component packages in vacuo.Incident light irradiation photocathode, photocathode is launched photoelectron in vacuum.Photoelectron enters dynode system under the focusing electrode electric field action, and amplifies by the multiplication that further Secondary Emission obtains.The electronics that anode is collected after amplifying is used as signal output.Photomultiplier can be divided into two types of end-window and side window types by the receive mode of incident light.Most of photomultiplier performances can be subjected to the influence in magnetic field, and magnetic field can make the emitting electrons in the photomultiplier break away from planned orbit and cause that gain loss, time response degenerate etc.This loss is relevant with the geometry of photomultiplier and the direction in magnetic field thereof.Distance from negative electrode to first dynode is long more, the optical window bore is big more, the just easy more influence that is subjected to magnetic field of photomultiplier.For example the magnetic field perpendicular to axial direction of 5G just can make optical window diameter 13mm, dynode be the photomultiplier output of linear focus type N when reducing to no magnetic field below 60%.
The general magnetic shield of being made by high permeability materials that adopts is eliminated the influence of magnetic field to photomultiplier.According to the line of magnetic induction law of refraction: from the little medium of magnetic permeability to the big medium of magnetic permeability, line of magnetic induction off-normal, from the big medium of magnetic permeability to the little medium of magnetic permeability, line of magnetic induction deflection normal.Thereby with the very big soft magnetic material (permalloy of magnetic permeability, ferrochrome etc.) magnetic shield of making, be placed in the magnetic field, because the magnetic permeability of magnetic shield is much larger than permeability of vacuum, magnetic resistance is much smaller than air reluctance, the overwhelming majority line of magnetic induction passes through in the wall of magnetic shield, and the cavity inside line of magnetic induction is few, and this has just reached the purpose of magnetic screen.
Design a magnetic shield, at first according to the intensity in conductively-closed magnetic field and the suitable magnetic shielding material of shielding target selection.Mainly consider the difficulty or ease, mechanical strength of relative permeability, saturation, price, processing and processing etc. when selecting magnetic shielding material.Relative permeability is high more, and the magnetic screen ability is strong more, but the general saturation point of material with high relative permeability is all lower, and saturated material does not have the effect of magnetic screen.After having selected shielding material, mainly consider aspects such as geometry, shape, size, continuity, closure, draw ratio, opening, MULTILAYER COMPOSITE shielding construction during the design shield.After magnetic screen machines, to carry out hydrogen anneal process, strictly observe the annealing cycle of defined, not only can guarantee to obtain best magnetic shield performance, but also the magnetic permeability of unannealed material on average can be improved 40 times.But after annealing, shield is carried out the shock and vibration test, will reduce the performance of material.
The maskable maximum field of present commercial photomultiplier magnetic screen has only tens Gausses, can't shielding strong magnetic field.Under high-intensity magnetic field, generally reduce the influence in magnetic field, but the detection efficient of photomultiplier reduces along with the increase of distance by the distance that increases photomultiplier and detected object; She Ji magnetic screen all is to rely on the thickness and the number of plies that increase magnetic shielding material to come shielding strong magnetic field voluntarily, have that volume is big, cost is high, shortcoming such as processing and difficult treatment, and the detection efficient of photomultiplier along with optical window before shielding material thickness increase and reduce, limited the application of photomultiplier.
Summary of the invention
At the general magnetic screen of present photomultiplier design can't shielding strong magnetic field problem, the purpose of this invention is to provide a kind of photomultiplier operate as normal under high-intensity magnetic field that makes, be used for the magnetic shielding device of the multi-layer compound structure of shielding strong magnetic field.
In order to realize purpose of the present invention, the magnetic shielding device that the present invention is used for the multi-layer compound structure of shielding strong magnetic field comprises as follows:
Adopt multi-layer compound structure, comprise three layers from outside to inside:
One silicon steel parts are the intermediate layer;
One alloy component is internal layer;
One solenoid coil is skin;
Alloy component is placed the silicon steel components interior, be equipped with solenoid coil in the outside of alloy component.
Description of drawings
Fig. 1 is the multi-layer compound structure magnetic shielding device schematic diagram that the present invention is used for shielding strong magnetic field
Fig. 2 is magnetic line of force distribution schematic diagram in magnetic shielding material and air
Fig. 3 is solenoid coil pictorial diagram among the present invention
Fig. 4 is a magnetic shielding cylinder pictorial diagram of the present invention
Fig. 5 a, Fig. 5 b concern external magnetic field and conductively-closed photomultiplier output amplitude, rise time
Fig. 6 a, Fig. 6 b are solenoid current and conductively-closed photomultiplier output amplitude, rise time variation relation under 115 Gauss's external magnetic fields
Embodiment
Below in conjunction with accompanying drawing the utility model is described in detail, be to be noted that described embodiment only is intended to be convenient to the understanding of the present invention, and it is not played any qualification effect.
The present invention is used for shown in the multi-layer compound structure magnetic shielding device schematic diagram of shielding strong magnetic field as Fig. 1, comprise silicon steel parts 1, alloy component 2, a solenoid coil 3, front end housing 4, rear end cap 5, nipple orifice 6, comprise three layers from outside to inside, outermost layer is a solenoid coil 3, the intermediate layer is silicon steel parts 1, innermost layer is an alloy component 2, and wherein silicon steel parts 1 adopt silicon steel material to make.Alloy component 2 adopts the permalloy material to make; Line solenoid 3 circles adopt copper core to make.
The both ends open of solenoid coil 3, silicon steel parts 1, the sealing of alloy component 2 one ends.
Gapped between solenoid coil 3 and the silicon steel parts 1.
Lead multilayer on the described solenoid coil 3 is close around arrangement, between layer and the layer, insulating barrier is arranged between the lead.
Described alloy component 2 interior diameters are greater than conductively-closed photomultiplier overall diameter.
The length of described alloy component 2 and silicon steel parts 1 are identical and be longer than four times of silicon steel parts 1 diameter.The draw ratio minimum is 4 times in the photomultiplier magnetic screen.
Described alloy component 2 body sidewalls and front end housing 4 are welded into as a whole.
Described rear end cap 5 is a movable end cover, is two layer composite structure, and internal layer is that permalloy layer, skin are the pure iron layer; The conductively-closed photomultiplier is disposed in alloy component 2 inside from rear end cap 5; Rear end cap 5 is connected with alloy component 2 size of main body; Rear end cap 5 has three nipple orifice 6, the working voltage that is used to draw the conductively-closed photomultiplier tube signal and inserts the conductively-closed photomultiplier.
Outermost layer solenoid coil 3 produces the magnetic field opposite with the high-intensity magnetic field direction, and high-intensity magnetic field is weakened significantly; Intermediate layer silicon steel parts 1 have higher magnetic field saturation, external magnetic field further is reduced to several Gauss, innermost layer permalloy parts 2 have very high low-intensity magnetic field permeability, further be reduced to very weak external magnetic field below the 0.001Gauss, far below the earth magnetic field level, guarantee the photomultiplier operate as normal.
Utilize solenoid coil 3 to produce the opposing magnetic field,,,, can significantly reduce the volume of magnetic screen and the consumption of magnetic shielding material conductively-closed magnetic field cancellation (weakening) with the magnetic field superposition of conductively-closed according to vector superposed principle.Place solenoid coil 3 according to the profile of conductively-closed photomultiplier and the direction in conductively-closed magnetic field, make the direction in solenoid coil 3 magnetic fields identical with the conductively-closed magnetic direction.Axially go up any magnetic field that a bit produces as the formula (1) in the solenoid coil 3, wherein n is that coil turn, I are electric current, β
1, β
2Be any and coil two ends angle on the axis.
The inner evenly head of district in the magnetic field that solenoid coil 3 produces, homogeneity range internal magnetic field intensity is B=μ
0NI can obtain magnetic field shielding effect preferably; Decay outside solenoid coil 3 soon in magnetic field, little to the influence of conductively-closed Distribution of Magnetic Field.
According to the magnetic induction law of refraction, the direction of place, the dielectric interface both sides magnetic flux density that relative permeability is different satisfies formula (2), wherein μ
1, μ
2Be the relative permeability of two media, α
1, α
2For the magnetic line of force in two media with the angle of normal.
Two kinds of medium magnetic permeabilitys of magnetic shielding material and air differ outstanding pearl, the relative permeability μ of air
1≈ 1, and μ
2Can reach thousands of even hundreds thousand of, thereby α
290 ° of ≈, α
10 ° of ≈, the magnetic line of force distribute as shown in Figure 2 in magnetic shielding material and air, and wherein 11,13 is air layer, and 12 is magnetic shielding material.Magnetic line of force line is almost parallel with interface in magnetic shielding material 12 matter, and very dense, μ
2Big more, α
2Approach 90 ° more, the magnetic line of force just approaches parallel with the surface more, thereby the magnetic flux outside draining to is more little, and promptly magnetic field intensity outside it, and then reaches the effect of magnetic screen in magnetic screen.When magnetic field intensity surpasses the saturation magnetic field value of its magnetic shielding material 12, the magnetic line of force that exceeds part will not change direction, and shielding properties descends.
High-intensity magnetic field decays to rapidly far below the earth magnetic field level at magnetic shielding device, guarantees photomultiplier operate as normal under high-intensity magnetic field.If the earth magnetic field is B
0, high-intensity magnetic field intensity is B
1, solenoid coil 3 magnetic fields are B
2, the magnetic shield saturation magnetic field is B
3, the magnetic shield attenuation coefficient is η, less than B
3Magnetic field all will be attenuated and be 1/ original η, after magnetic shielding cylinder annealing, to satisfy B
3/ η is much smaller than B
0η determines jointly by factors such as the structure of magnetic shielding material, magnetic shield, processing technologys, is different for the η in the magnetic field of a magnetic shield different directions.Therefore regulate solenoid coil 3 directions, make it axially consistent, regulate the electric current of solenoid coil 3, make with the high-intensity magnetic field direction | B
1-B
2|≤B
3, can guarantee conductively-closed photomultiplier operate as normal.After the magnetic shielding device shielding, the magnetic field intensity of conductively-closed photomultiplier working region can be represented with (3) formula:
From top analysis as can be seen, by regulating the direction and the electric current of solenoid coil 3, high-intensity magnetic field is reduced, the magnetic field after the reduction decays to much smaller than the earth magnetic field level through magnetic shielding cylinder.This multi-layer compound structure is compared with existing magnetic screen, and the maskable magnetic field intensity is higher, and the highfield that is shielded is not limited by the saturation magnetic field of magnetic shielding material.There are problems such as coil current is excessive, caloric value height during the screening electrode high-intensity magnetic field, can solve by outside solenoid coil 3, suitably increasing measures such as one deck silicon steel parts 1 and water-cooled.Shield the same magnetic field magnetic shielding material still less, the volume of magnetic screen is littler, the difficulty that greatly reduces processing and handle.
The present invention can shielding strong magnetic field, has solved the problem that maskable maximum magnetic field strength in the existing magnetic screen design is subjected to materials limitations.
The present invention uses less magnetic shielding material, obtains best Magnetic Shielding Effectiveness under high-intensity magnetic field, and is simple with general high-intensity magnetic field shielding structure compared, volume is little, be convenient to processing and handle, and is more economical.
The embodiment that the present invention uses is: select for use to be applied in the slow positron lifetime measurement, specific embodiment is as follows:
The photomultiplier of process magnetic screen places the end of positron beam streamline, measures the gamma-rays that positron annihilation produces, and shielding is to liking 100 Gausses' the magnetic field that transports.
Interior diameter 68mm, the overall diameter 86mm that solenoid coil 3 is selected, winding wire footpath 1.3mm, length 200mm, the internal diameter of solenoid coil 3 be greater than the magnetic shielding cylinder external diameter, as Fig. 3 for shown in the solenoid coil pictorial diagram among the present invention.Therefore the heating meeting of solenoid coil 3 impacts the conductively-closed photomultiplier when considering work, adds heat-barrier material as poly-tetrafluoro etc. between solenoid coil 3 and magnetic shielding cylinder.
Alloy component 2 is selected permalloy or other alloy material, and alloy component 2 interior diameters are chosen as 57mm, overall diameter is chosen as 59mm; Front end housing 4 is selected permalloy or other alloy material, and front end housing 4 thickness are chosen as 1mm; Silicon steel parts 1 adopt silicon steel sheet, and silicon steel sheet thickness is chosen as 1mm.
Shown in Fig. 4 magnetic shielding cylinder pictorial diagram of the present invention, it is on the circumference of center of circle diameter 30mm that rear end cap 5 opening diameter 10.5mm, rear end cap 5 perforates are distributed on the end cap center; The pure iron layer thickness of rear end cap 5 is that the permalloy layer thickness of 1mm, rear end cap 5 is 1mm.
The conductively-closed photomultiplier that adopts is the R3377 of shore pine company, and crystal is the BF of φ 30 * 10
2Crystal, the conductively-closed photomultiplier is encapsulated in the magnetic shielding cylinder, as the cone of conductively-closed photomultiplier, conductively-closed photomultiplier and bleeder circuit are fixed on the end cap magnetic shielding cylinder simultaneously, and the top of conductively-closed photomultiplier is apart from magnetic shielding cylinder top 20mm.The relative permeability of all parts is all near 1 in the magnetic shielding cylinder.
(TDS3052B TEK) observes conductively-closed photomultiplier transit tube anode output signal, the relatively variation of following pulse rise time of different situations and amplitude to utilize oscilloscope.
Having only under earth magnetic field, the solenoid coil 3 no current situations, remove rear end cap 5, measure remnant field in the tube, remnant field is 1/600 of earth magnetic field.
Owing to mainly be that shielding transports magnetic field, therefore solenoid coil 3 and magnetic shielding cylinder concentric are placed.Progressively increase axial magnetic field, the output pulse rise time of conductively-closed photomultiplier, changes in amplitude from figure as can be seen, use magnetic shielding cylinder can't shield axial magnetic field greater than 60 Gausses separately shown in Fig. 5 a and Fig. 5 b.
With big coil magnetic field stuck-at-15 Gausses, increase the electric current of solenoid coil 3 gradually, the rise time of conductively-closed photomultiplier transit tube anode output pulse, changes in amplitude are shown in Fig. 6 a and Fig. 6 b.Along with the increase in solenoid coil 3 magnetic fields, the conductively-closed photomultiplier begins that output is arranged, and reduces gradually pulse rise time, pulse amplitude increases gradually.
From experimental result as can be seen magnetic shielding cylinder can shield 60 gauss magnetic fields, make conductively-closed photomultiplier operate as normal; Magnetic field greater than 60 Gausses can drop under 60 Gausses by the electric current of regulating solenoid coil 3, guarantees conductively-closed photomultiplier operate as normal.Regulate the electric current of solenoid coil 3, make external magnetic field far below 60 Gausses, at this moment the magnetic field at conductively-closed photomultiplier place is about 0.001 Gauss, can make the performance of conductively-closed photomultiplier reach best.
Although described the present invention by the foregoing description, the present invention is not limited to this embodiment.Therefore, do not depart from the various equivalent structures of spirit of the present invention, should replace composite construction etc. as outside solenoid coil 3, increasing one deck pure iron layer or silicon steel layer, multi-thread ring layer and many pure iron layer or silicon steel within the scope of the present invention yet.
Claims (10)
1. a magnetic shielding device that is used for the multi-layer compound structure of shielding strong magnetic field is characterized in that, adopts multi-layer compound structure, comprises three layers from outside to inside:
One silicon steel parts (1) are the intermediate layer;
One alloy component (2) is internal layer;
One solenoid coil (3) is skin;
Alloy component (2) is placed silicon steel parts (1) inside, be equipped with solenoid coil (3) in the outside of alloy component (2); The solenoid coil (3) that is connected with certain electric current produces the armoured magnetic field opposite with outer magnetic field direction, according to the magnetic vector principle of stacking, conductively-closed magnetic field is offset significantly, the characteristics that have higher magnetic field saturation according to intermediate layer silicon steel parts (1), external magnetic field is further reduced, utilize innermost layer permalloy parts (2) to have the characteristic of very high low-intensity magnetic field permeability again, very weak external magnetic field further is reduced to far below the earth magnetic field level; Its axial direction of solenoid coil (3) should be consistent with the high-intensity magnetic field direction, and its size of current satisfies | B
1-B
2|≤B
3, can be made the magnetic field intensity in conductively-closed zone reach the different levels that require by internal layer silicon steel parts (1) and further shielding of permalloy parts (2) to guarantee the magnetic field intensity after the counteracting, wherein, B
1Expression high-intensity magnetic field magnetic field intensity, B
2Magnetic field intensity, B that expression solenoid coil (3) produces
3Expression magnetic shield saturation magnetic field intensity.
2. magnetic shielding device as claimed in claim 1 is characterized in that: solenoid coil (3), silicon steel parts (1), alloy component (2) adopt cylindrical structure.
3. magnetic shielding device as claimed in claim 1 is characterized in that: the both ends open of solenoid coil (3), silicon steel parts (1), the sealing of alloy component (2) one ends.
4. magnetic shielding device as claimed in claim 1 is characterized in that: gapped between solenoid coil (3) and the silicon steel parts (1).
5. magnetic shielding device as claimed in claim 1 is characterized in that: silicon steel parts (1) are close to alloy component (2) outside.
6. magnetic shielding device as claimed in claim 1 is characterized in that: the lead multilayer on the described solenoid coil (3) is close around arrangement, between layer and the layer, insulating barrier is arranged between the lead.
7. magnetic shielding device as claimed in claim 1 is characterized in that: described alloy component (2) interior diameter is greater than conductively-closed photomultiplier overall diameter.
8. magnetic shielding device as claimed in claim 1 is characterized in that: the length of described alloy component (2) is identical with silicon steel parts (1) and be longer than four times of silicon steel parts (1) diameter.
9. magnetic shielding device as claimed in claim 1 is characterized in that also comprising: alloy component (2) body sidewall is connected with front end housing (4).
10. magnetic shielding device as claimed in claim 1 is characterized in that, also comprises rear end cap (5):
Described rear end cap (5) is a movable end cover, is two layer composite structure, and internal layer is that permalloy, skin are pure iron;
The conductively-closed photomultiplier is disposed in alloy component (2) inside from rear end cap (5);
Rear end cap (5) is connected with alloy component (2) size of main body;
Rear end cap (5) has three nipple orifice (6), the working voltage that is used to draw the conductively-closed photomultiplier tube signal and inserts the conductively-closed photomultiplier.
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| CNB2006101138245A CN100546452C (en) | 2006-10-18 | 2006-10-18 | A kind of magnetic shielding device that is used for the multi-layer compound structure of shielding strong magnetic field |
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| CN105161140A (en) * | 2015-09-02 | 2015-12-16 | 北京控制工程研究所 | Charged particle shielding device of space optical detector based on electromagnetic complex fields |
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| CN103415196B (en) * | 2013-08-07 | 2016-06-22 | 北京航空航天大学 | A kind of small-sized nonmagnetic atom shielding and magnetic actuation means |
| CN103870701A (en) * | 2014-03-24 | 2014-06-18 | 东南大学 | Optimal modeling method for magnetic shielding barrel parameters of atom magnetometer/atom gyroscope |
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| CN109239624B (en) * | 2018-08-30 | 2021-01-19 | 江苏赛诺格兰医疗科技有限公司 | Test system and test method for detecting magnetic shielding performance of magnetic shielding material |
| CN110416057B (en) * | 2019-07-31 | 2022-03-01 | 深圳麦科田生物医疗技术股份有限公司 | Photomultiplier shielding structure and signal detection device |
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| US4152745A (en) * | 1977-04-11 | 1979-05-01 | Eul Edward A | Magnetic shield device |
| US5951459A (en) * | 1997-08-29 | 1999-09-14 | Orthosoft, L.L.C. | Magnetic coil for pulsed electromagnetic field |
| US20060055402A1 (en) * | 2004-09-10 | 2006-03-16 | Yusuke Seki | Magnetic shielding apparatus and biomagnetism measuring device |
-
2006
- 2006-10-18 CN CNB2006101138245A patent/CN100546452C/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4152745A (en) * | 1977-04-11 | 1979-05-01 | Eul Edward A | Magnetic shield device |
| US5951459A (en) * | 1997-08-29 | 1999-09-14 | Orthosoft, L.L.C. | Magnetic coil for pulsed electromagnetic field |
| US20060055402A1 (en) * | 2004-09-10 | 2006-03-16 | Yusuke Seki | Magnetic shielding apparatus and biomagnetism measuring device |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105161140A (en) * | 2015-09-02 | 2015-12-16 | 北京控制工程研究所 | Charged particle shielding device of space optical detector based on electromagnetic complex fields |
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