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Storage Ring

Design and operation parameters of the MLS storage ring

The MLS is designed as a dedicated UV/VUV source. The available low energy spectra from the bending magnets as well as from an undulator perfectly complement the spectra available at BESSY II. Moreover, the MLS can be operated in a so-called low-α mode for the generation of coherent synchrotron radiation in the FIR/THz spectral range via short electron bunches. Essential for PTB is the operation of the storage ring as a primary source standard. Therefore a high stability and reproducibility of the storage ring settings is required as well as equipment for the precise determination of the storage ring parameters.

The MLS has a circumference of 48 m and is designed as an asymmetric double-bend achromate with twofold symmetry. Each of the eight 45˚ bending magnets can be equipped with two front ends. The MLS has two long and two short straight sections. The long straight section can accommodate undulators of the BESSY II design which enables PTB to operate its U125 undulator. Injection will be effected from a 105 MeV microtron, the electron energy is then ramped to the desired value. The electron energy can be chosen in the range from 105 MeV to 630 MeV, i. e. the characteristic energy can be tuned in the range from 1.7 eV up to 364 eV in order to adjust the spectral shape to the requirements of the calibration task. The electron beam current can be adjusted in a range of more than 11 orders of magnitude, i. e. from a single electron (1 pA) up to 200 mA, in order to comply with the dynamic range of a device to be calibrated.

ParameterValue
lattice structuredouble bend achromat
circumference48 m
electron energy105 MeV to 630 MeV
magnetic induction of bending magnet0.43 T to 1.3 T
characteristic wavelength3.4 nm to 735 nm
characteristic photon energy1.7 eV to 364 eV
electron beam current1 pA to 200 mA
natural emittance (600 MeV)100 nm rad
injection energy 105 MeV