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TY - CONF AU - González, N AU - Colldelram, C. AU - Escudero, C. AU - Ferrer, S. ED - Casas, Joan ED - Schaa, Volker RW ED - Costa, Isidre ED - López, David ED - Prieto, Montserrat TI - High Frequency UHV Mechanical X-Ray Beam Chopper J2 - Proc. of MEDSI2016, Barcelona, Spain, 11-16 September 2016 CY - Barcelona, Spain T2 - Mechanical Engineering Design of Synchrotron Radiation Equipment and Instrumentation Conference T3 - 9 LA - english AB - A mechanical chopper* has been designed and built to perform X-ray Absorption Spectroscopy (XAS) experiments with operating liquid electrochemical cells at NAPP end station of ALBA Synchrotron (BL24, CIRCE). When operating the cell, to separate the weak currents induced by the X-ray absorption process at the electrode in contact with the electrolyte (TEY signal) from the faradaic current set between the electrodes, the incoming beam must be chopped at a certain frequency (w). Then, using a lock in amplifier, the signal at this frequency w can be extracted and measured. When the chopper is located in the beam path, it produces pulses with a frequency w, modulating the TEY signal. The chopper developed at ALBA, with variable frequency, improves previous designs which used piezo-actuated choppers constrained to work at fixed oscillating frequencies**. The design consists of a slotted disk that spins around an axis by means of an UHV stepper motor. A LED and photodiode based UHV sensor ensures that frequency drifts do not affect the measurements. The motor is hold by an internally water cooled OFHC support, which allows long duration experiments at high speeds without stopping. PB - JACoW Publishing CP - Geneva, Switzerland SP - 339 EP - 341 KW - ion KW - vacuum KW - experiment KW - electron KW - controls DA - 2017/06 PY - 2017 SN - 978-3-95450-188-5 DO - doi:10.18429/JACoW-MEDSI2016-WEPE15 UR - http://jacow.org/medsi2016/papers/wepe15.pdf ER -