Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
  • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
  • G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
  • G21K1/04—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using variable diaphragms, shutters, choppers
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
  • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
  • G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
  • G21K1/04—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using variable diaphragms, shutters, choppers
  • G21K1/043—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using variable diaphragms, shutters, choppers changing time structure of beams by mechanical means, e.g. choppers, spinning filter wheels

Definitions

• the invention relates to a chopper for a particle beam.
• a chopper is an element that has both particle-beam transmissive and particle-beam impermeable regions. When the chopper is moved through the particle beam, mutually permeable and impermeable regions pass through the particle beam so that the particle beam is modulated.
• peripheral speeds of about 300 m / s are required.
• the document discloses both designed as solid disks and spoke-shaped segmented chopper to achieve such rotational speeds.
• This chopper is characterized by at least one annular, in particular annular, guide element and by at least one control element for the particle beam, which is mounted against the guide element such that at least one point on the control element is able to circulate along a circumference of the guide element.
• a guide element in the sense of this invention is understood to be an element which imposes one or more constraints on the movement of the control element.
• the guide element should therefore at least be designed and / or fixed in space such that a movement of the control element during operation of the chopper does not trigger any movement of the guide element.
• a control element is understood to be any element which has at least one region which is able to attenuate the intensity of the particle beam. In particular, this region can be completely impermeable to the particle beam. If the control is moved by the particle beam, the intensity of the particle beam can be modulated.
• the storage according to the invention along a circumference is considerably more stable than the storage on an axis of rotation which is necessarily required in the case of wheel-shaped choppers according to the prior art.
• a much smaller force is required than when mounted on a rotation axis.
• the bearing force 5 to be applied can be distributed over the entire circumference of the guide element, so that overall higher bearing forces can be exerted on the control element.
• the guide element can have a higher circumference and at the same time the control can be moved faster.
• the control can move at a higher peripheral speed. This causes o the particle beam can be modulated at a higher frequency than was possible in the prior art.
• the invention expressly includes a chopper wheel as a control element, wherein this may be formed as a solid disc or spoke-shaped segmented and wherein also a bearing can be present on a rotation axis. 5
• a chopper wheel as a control element, wherein this may be formed as a solid disc or spoke-shaped segmented and wherein also a bearing can be present on a rotation axis. 5
• an existing chopper can be retrofitted with the storage according to the invention along a circumference.
• the benefits according to the invention thus also come into effect in that, in order to compensate for a given disturbing moment, the bearing must apply less force along the circumference than the bearing on an axis of rotation and that altogether higher bearing forces can be exerted on the control element. Since the control is mounted according to the invention close to the place of its function, the lever with which disturbance torques can attack the bearing, advantageously shortened.
• a given disturbance torque acts with a lower force on the bearing than when stored on a rotation axis according to the prior art.
• the danger is reduced that the bearing will be destroyed and the control or parts thereof fly away uncontrolled, for example, when the movement of the control is stopped abruptly by a foreign body.
• a rotary axis is unnecessary altogether. There is thus no need to mechanically connect parts of the control element with a rotation axis.
• various shapes for the control are possible. It may, for example, annular, in particular annular, be formed.
• the control can be arranged concentrically to the guide element.
• the effect on the particle beam can be achieved even with a single control element, which is just large enough to attenuate the particle beam at a point of rotation around the circumference of the guide element.
• a control can be composed, which is able to circulate as a whole around the circumference of the guide member. This control can, for example, occupy all or part of the circumference of the guide element.
• the individual control elements can then be replaced independently of one another.
• the connection of the individual control elements can be elastic or solid.
• Such shapes of the control can have a considerably lower weight than prior art chopper wheels. This weight also only grows linearly with the size of the control. Since the decisive for the maximum achievable modulation frequency peripheral speed is the product of speed and scope, the largest possible extent of the control is advantageous.
• the weight is proportional to the area and thus grows quadratically with the circumference.
• the significantly lower weight according to the invention in turn causes, per unit bearing force, which on the Steuerele- ment can be exercised, a higher peripheral speed and thus a higher modulation frequency can be achieved.
• the lower weight improves the reliability of the chopper in two ways: it leads to a lower stress of the control by the centrifugal forces, so that the risk is reduced that this tears.
• the fragments In the unlikely event of tearing, the fragments also have a much lower mass and thus kinetic energy, so that a much lower effort for an enclosure must be driven, which protects the environment from such fragments.
• the lower weight also increases the natural frequencies of the control element so that they are advantageously no longer in the range of the circulating frequencies around the circumference of the guide element.
• annular shape of the control affects yet another advantageous manner. Only the guide element and the control must be in vacuum, but not the entire area bounded by these elements. It is thus sufficient if a tubular region which encloses the control and the guide element is kept under vacuum. In particular, this region can be arranged between an inner diameter which is smaller than the inner diameter of the control element and an outer diameter which is greater than the outer diameter of the guide element. This dramatically reduces the volume to be vacuumed. The cost of pump power and time for the production of this vacuum is reduced considerably.
• the ring shape of the guide element according to the invention is not fixed to the circular ring shape.
• Other annular designs, such as ellipses, may be advantageous, for example, if the chopper is to be adapted to tight spatial conditions of an already existing experimental setup.
• control element has at least one region which is reflective for the particle beam.
• a graphite monocrystal is suitable for a neutron beam. Then the portion of the particle beam not transmitted by the chopper can be used for another experiment. But he can also be led by another chopper. If both branches of the particle beam are combined with each other, the result is modulated at a higher frequency than a single chopper could
• control element has at least one helical bore.
• the chopper then not only modulates the intensity of the particle beam, but also simultaneously selects the particles of the beam according to their velocity and thus their energy and momentum.
• chopper and speed selector are advantageously combined in one device. Since only one drive is required, such a combination device is more reliable than two individual devices. At the same time installation space is saved, which is particularly advantageous in space-constrained experimental arrangements and when operating in a vacuum.
• control element is supported against the guide element in such a way that the receptor point can circulate along the outer circumference of the guide element.
• control element is mounted against the guide element such that the point of view is capable of circulating along the inner circumference of the guide element.
• the control is pressed in operation by the centrifugal forces against the guide element. This increases the stability of the storage and at the same time also the operational safety: Even if the control should break, the guide element prevents the fragments from the radial fly away. A separate, elaborate enclosure of the chopper to protect the environment from debris is not required. The guide element already increases operational safety.
• the storage of the control element against the guide element is in a particularly advantageous embodiment of the invention, a magnetic storage and in particular a permanent magnetic storage.
• a magnetic storage and in particular a permanent magnetic storage Such storage is non-contact and thus wear-free even at high speeds. No lubricant is required so that the bearing is fully ultra high vacuum compatible.
• the guide element and the control element each have at least one magnetized region in such a way that these magnetized regions repel each other at the point of circulation of the point in which they come closest.
• the control element has an annular shape and the magnetized areas are arranged point-symmetrically about the center of the ring, a rest position is defined in which all repulsions between magnetized areas are compensated. In a deflection from the rest position, a magnetic gap is reduced, so that the repulsive force between the corresponding magnetized areas increases and drives the control back to the rest position.
• the bearing of the control on constraints in such a way that the control can neither move axially out of the guide element or tilt in this.
• This can be effected, for example, by additional magnetized areas on the control element and on the guide element, which, when in operation directly opposite one another, exert magnetic forces with an axial component on one another.
• the guide comprises means for generating a magnetic traveling field. Then can in addition to the magnetic bearing and the drive of the control via the guide element take place.
• This functional integration of drive and bearing is also able to respond to imbalances in the control by adjusting the strength of the traveling magnetic field over time. Such imbalances are very difficult to avoid in choppers with typical diameters of 1, 20 m and more and peripheral speeds up to 300 m / s.
• At least one temporarily or permanently magnetized region of the guide element which belongs to the magnetic bearing of the control element against the guide element, at the same time also an element for generating the magnetic traveling field.
• the magnetized region is, for example, a coil which is energized for magnetic storage of the control element according to a time program, an additional current can be modulated onto this current, which generates the traveling magnetic field.
• the magnetic traveling field is advantageously perpendicular to the magnetic field of the magnetic bearing.
• the approach offers a possibility to modify in the prior art by elements rotating around a rotation axis, which achieve a physical effect in the region of their outer periphery, in such a way that the ele- ment is stored along the outer circumference.
• the axis of rotation and connections of any kind between this axis of rotation and the outer circumference can be partially or completely saved.
• the mass of the arrangement can advantageously be reduced, and the lever with which disturbing moments act on the bearing is advantageously reduced.
• the outer circumference can be tailored to the needs. It may for example be a closed loop, which may be arbitrarily oriented in space, for example in a vertical plane.
• the bearing carries the physical effect-achieving element, such as one or more turbine blades, beam stopper, filters, reflectors or energy selectors.
• turbomolecular pump and the exhaust gas turbocharger are characterized by particularly large disturbance torques which engage in a magnetic bearing on a shaft according to the prior art with a large lever on the camp.
• the bearing force is distributed over the entire circumference of the second component, so that according to the invention overall significantly greater bearing forces can be absorbed than in the prior art.
• the volume of construction of both turbomolecular pumps and exhaust gas turbochargers can be advantageously reduced by the inventive integration of drive and storage.
• Figure 1 exemplary embodiment of the chopper according to the invention along which
• FIG. 2 side view of the chopper from FIG. 1.
• FIG. 3 section of the chopper from FIG. 1 in sectional drawing.
• FIG. 4 Three-dimensional view of the chopper from FIG. 1.
• FIG. 1 shows an exemplary embodiment of a chopper according to the invention in a view along its axis of symmetry (the axis of symmetry is perpendicular to the plane of the drawing).
• This chopper comprises an annular guide element 11 on a base 12 as well as a likewise annular, concentric with the guide element 1 1 arranged control element 13.
• the guide member 11 comprises a main body I Ia and solenoid I Ib.
• the main body I Ia consists of a circular ring 1 IaI, which is arranged between two annular discs 1 Ia2 and 1 Ia3.
• the magnetic coils 1 Ib are sunk at regular intervals in the inner side of the circular ring 1 IaI of the main body 1 Ia.
• the control element 13 comprises a base ring 13a, permanent-magnetic regions 13b and regions 13c which are reflective for the particle beam and thus impermeable.
• the permanent magnetic regions 13b are sunk at regular intervals in the outer side of the base ring 13a.
• the regions 13c reflecting and thus impermeable to the particle beam are mounted at regular intervals on the inside of the base ring 13a.
• the magnetic coils Ib and the permanent magnetic regions 13b cooperate in such a way that the control element 13 is mounted magnetically against the guide element 11.
• the magnetic coils 1b are also elements for generating a traveling magnetic field with which the control element 13 and thus also the regions 13c reflecting the particle beam can be set into rotation within the guide element 11.
• the main body 11a encloses the base ring 13a almost completely except for a radially inwardly directed region in which the particle-beam-reflecting regions 13c can protrude radially inwards around the guide element 11 in each circulating position of the control element 13.
• the magnetic bearing of the control member 13 is supplemented against the guide member 11 by a mechanical emergency storage, which imposes such constraints on the control 13 that it can neither move axially out of the guide member 11 nor tilt in this
• Figure 2 shows a side view of the chopper of Figure 1. Compared with Figure 1, the chopper is here rotated by 90 ° out of the plane. Here, the subdivision of the main body 11a into a circular ring 11a, as well as two annular disks 11a2 and 11a3, is illustrated.
• FIG. 3 a section of the chopper is shown in cross-sectional view, wherein the section along the line A-A in Figure 1 was performed.
• the annular discs 1 Ia2 and 1 Ia3 of the main body I Ia have at their directed to the common axis of symmetry of guide member 11 and control element 13 edge
• extensions 1, Ia4, and 1, 5a which are directed toward one another.
• the projections 1 Ia4 and 1 Ia5 form a gap 1 Ia6, in which engages the particle beam for the reflecting portion 13c of the control and in which this region 13c can rotate.
• the magnetized region 13b which is recessed in the base ring 13a of the control element, forms a magnetic gap with the magnetic coil 11b.
• the magnetized region 11a7 forms a magnetic gap with the magnetized region 13al.
• the magnetized region 1 la ⁇ forms a magnetic gap with the magnetized region 13 a 2.
• the region 13c which is reflective for the particle beam and thus impermeable receives its reflective property by means of a coating 13cl applied on one side.
• the magnetized regions 13b buried in the base ring 13a of the control element 13 may be additionally secured by a layer or winding of high strength material (such as CFIC or a fabric) extending radially outwardly prevent directed movement of the magnetized portions 13b out of the base ring 13a out.
• high strength material such as CFIC or a fabric
• FIG. 4 shows the chopper in a three-dimensional representation. It can be seen particularly clearly that the regions 13c reflecting the particle beam, during operation, within the gap 11a6 between the extensions 11a4 and 1 Ia5 of the annular disks 1 Ia2 and 1 Ia3 of the base body 1 Ia of the guide member 11 rotate.

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• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Magnetic Bearings And Hydrostatic Bearings (AREA)
• Mechanical Light Control Or Optical Switches (AREA)
• Analysing Materials By The Use Of Radiation (AREA)
• Motorcycle And Bicycle Frame (AREA)
• Particle Accelerators (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 2007
  • 2007-09-28 DE DE102007046739A patent/DE102007046739A1/de not_active Withdrawn
• 2008
  • 2008-09-12 CN CN2008801096502A patent/CN101809676B/zh active Active
  • 2008-09-12 EP EP08801331A patent/EP2198432B1/fr active Active
  • 2008-09-12 AT AT08801331T patent/ATE501513T1/de active
  • 2008-09-12 JP JP2010526159A patent/JP5431332B2/ja active Active
  • 2008-09-12 US US12/733,496 patent/US8324590B2/en active Active
  • 2008-09-12 DE DE502008002832T patent/DE502008002832D1/de active Active
  • 2008-09-12 WO PCT/DE2008/001539 patent/WO2009039832A1/fr active Application Filing

Non-Patent Citations (1)

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