Instrument for moving and positioning of optical elements with nanometric mechanical stability and resolution in synchroton light source beamlines

Abstract

An instrument for moving and positioning of an optical element in beamlines comprises a mounting structure to which one (or more) optical element(s) is mounted, as well as a reference structure, in relation to which the mounting structure is moved by means of a moving means of low (or close to zero) mechanical stiffness and in relation to which the position of the mounting structure is metered by means of a high-resolution interferometer. The invention proposes that the instrument also comprises a balance mass for receiving the reaction force from the moving means of the mounting structure, and both the mounting structure and the balance mass are attached to the reference structure by spring means, with specific stiffness properties, allowing the positioning control of the mounting structure to be done by a control system with main feedback loop with high bandwidth (>100 Hz). In order to allow for a broader range of movement between the mounting structure and the reference structure, by means of a cascaded movement, the instrument may further comprise an intermediate structure attached to the reference structure, also preferably by spring means with specific stiffness properties, the complementary structure receiving the mounting structure and the balance mass in place of the reference structure. Such an instrument may be embodied in a new-generation synchrotron light source beamline mounted double-crystal monochromator, being sufficient for this that the spring means to be conveniently chosen, the reference structure to have a main rotation in relation to the incident beam, and in addition to the crystal mounted to the mounting structure, a complementary crystal to be mounted to the complementary mounting structure rigidly attached to the reference structure.

1 . An instrument for moving and positioning of optical elements with nanometric mechanical stability in synchrotron light sources beamlines, comprising:
 a reference structure;   a mounting structure, to which the optical element(s) is mounted and is attached in a movable manner to the reference structure, allowing for its relative movement in one or more directions or rotations;   a moving means for movement of the mounting structure in relation to the base;   at least one balance mass, also attached in a movable manner to the reference structure, allowing for the relative movement in one or more directions of rotation, as well as the mounting structure, and receiving the reaction force resulting from the positioning of the mounting structure in relation to the reference structure, through the actuation of the moving means;   an interferometer measuring the position of the mounting frame in relation to the reference structure;   a main feedback loop including interferometer and the moving means, in which the interferometer information is utilized to control the position of the mounting structure through the moving means.   
     
     
         2 . The instrument, according to  claim 1 , consisting essentially of the mounting structure which is attached to the main structure by a first spring means. 
     
     
         3 . The instrument, according to  claim 2 , consisting essentially of the balance mass which is attached to the main structure by a second spring means. 
     
     
         4 . The instrument, according to  claim 3 , consisting essentially of the stiffness characteristics of the first spring means to be equal to the stiffness characteristics of the second spring means, allowing for the translations and rotations of interest (free degrees of freedom) of the mounting structure and of the balance mass, respectively, in relation to the reference structure, limiting complementary translations and rotations (restricted degrees of freedom). 
     
     
         5 . The instrument, according to  claim 4 , consisting essentially of the moving means being Lorentz type actuators (voice-coils), comprises a minimum number of actuators equal to the number of free degrees of freedom of the mounting structure and of the balance mass. 
     
     
         6 . The instrument, according to  claim 5 , wherein the interferometer consists of a minimum number of position sensors equal to the number of free degrees of freedom of the mounting structure and of the balance mass. 
     
     
         7 . The instrument, according to  claim 6 , consisting essentially of the instrument further comprising a complementary structure, attached in a movable manner to the main structure, and a moving means for moving of the complementary structure in relation to the reference structure. 
     
     
         8 . The instrument, according to  claim 7 , consisting essentially of the mounting structure and the balance mass being attached by the first and second spring means to the complementary structure rather than directly to the base, that is, with the complementary structure becoming an intermediate moving element (cascaded) between the mounting structure and the reference structure. 
     
     
         9 . The instrument, according to  claim 8 , consisting essentially of the complementary structure being attached to the reference structure by a third spring means. 
     
     
         10 . The instrument, according to  claim 6 , consisting essentially of each of the first, second and/or third spring means being comprised of a leaf spring or of a set of (combination) leaf springs. 
     
     
         11 . The instrument, according to  claim 1 , comprising the reference structure that has a main rotation axis (x-axis), perpendicular to the direction of propagation of the incident beam in the beamline (z-axis). 
     
     
         12 . The instrument, according to  claim 1 , comprising the complementary structure that is movable in relation to the reference structure only in the direction perpendicular (y′-axis) to the rotation axis of the reference structure (x-axis), in a way that the third set of leaf springs is less rigid in the direction of offset (y′-axis), but quite rigid in the two other perpendicular directions (x- and z′-axes) and in relation to the rotations of to the reference structure (Rx, Ry′ Rz′ rotations). 
     
     
         13 . The instrument, according to  claim 12 , consisting essentially of the mounting structure which is movable in relation to the complementary structure in only one translation (y′-axis), in parallel with the moving direction of the complementary structure in relation to the main structure, and two more rotations (Rx and Rz′ rotations), around the axes perpendicular (x- and z′-axes) to translation axis (y′-axis), in a way that the third set of leaf springs is less rigid in the direction of translation (y′-axis) and in the two rotations perpendicular to it (Rx and Rz′ rotations), but rigid in the two directions perpendicular (x′- and z′-axes) to the direction of offset (y′-axes), as well as rigid in the rotation around it (Ry′ rotation). 
     
     
         14 . The instrument, according to  claim 13 , consisting essentially of the balance mass which is movable in relation to the complementary structure in only one translation (y′-axis), in parallel with the moving direction of the complementary structure in relation to the main structure, and two more rotations (Rx and Rz′ rotations), around the axes perpendicular (x- and z′-axes) to the axis of translation (y′-axis), such that the second set of leaf springs is less rigid in the direction of translation (y′-axis) and in the two rotations perpendicular to the moving direction (Rx and Rz′ rotations), but rigid in the two directions perpendicular (x′- and z′-axes) to the direction of offset (y′-axes), as well as rigid in the rotation around it (Ry′ rotation). 
     
     
         15 . The instrument, according to  claim 14 , comprising an additional complementary mounting structure, rigidly fixed to the reference structure, and a complementary optical element, rigidly mounted to the complementary mounting structure. 
     
     
         16 . The instrument, according to  claim 15 , consisting essentially of the positioning sensor that measures the position of the mounting structure in relation to the additional complementary mounting structure, rather than in relation to the reference structure, allowing for a better positioning accuracy between the optical element and the complementary optical element. 
     
     
         17 . The instrument, according to  claim 16 , wherein the instrument is a double-crystal monochromator and the optical element and the complementary optical element are diffraction crystals, the first one being rigidly mounted to the mounting structure and the second one being rigidly mounted to the complementary mounting structure. 
     
     
         18 . The instrument, according to  claim 17 , consisting essentially of the optical element and the complementary optical element comprised of multiples pairs of crystals with distinct characteristics, with an element of each pair rigidly mounted to the mounting structure and to the complementary mounting structure. 
     
     
         19 . The instrument, according to  claim 6 , consisting essentially of the positioning sensors of the interferometer comprising interferometric offset sensors, with high reading rates and subnanometric resolutions.