Cerdanyola del Vallès, 27th July 2020 The commissioning time on 24th and 25th July has been used to bring the first synchrotron radiation into LOREA beamline. On Friday 24th the front end (inside the tunnel, connecting the storage ring to the beamline) has been opened to transfer the radiation, produced by the insertion device (an elliptical polarization undulator, EPU125), on the first optical element of the beamline, M1, placed inside the optical hutch, for the first time. M1 is a planar mirror, its main function is to absorb the thermal power of synchrotron radiation. In fact, it brings thermal power (not useful, it’s only heat) together with a high flux of photons. Most of the photon flux is reflected by M1 into the beamline (between 95% and 60%, depending on the photon energy), it passes through a beam defining slit and can be observed with the use of a fluorescent screen, placed outside the optical hutch. The remaining part of photons and heat is absorbed by this mirror, which is internally cooled by water.
Commissioning started on Friday morning at 8 am, with the opening of the front end and the immediate observation of a luminescent spot in the fluorescent screen monitor, without any need of aligning the beamline elements.
The spot on the fluorescent screen was produced by the continuous synchrotron radiation produced by the magnets of the storage ring. The current of the storage ring was initially very low (2 mA) to have a low power of radiation. The mirror, while absorbing thermal power, started to outgas the chemical species absorbed on its surface (condensed water, moisture, absorbed nitrogen, for example) and the pressure in the vacuum chamber slightly increased. Pressure and temperature were constantly checked while the ring current was improved without producing a too high increase of neither of them, because it would have been detrimental for the surface integrity of the mirror. At the end of the first commissioning day, the ring current reached the nominal value of 250mA without any major issue, following the commissioning plan.
On the second day, the ring current was maintained at 250mA, and the insertion device was slowly and carefully set to the nominal values of the beamline operation.
Left: Image of the radiation produced by the insertion device of LOREA with the ring current of 250mA and the undulator gap of 145mm. Right: Image of the radiation produced by the insertion device of LOREA (right middle) and by the bending magnet (left bottom) with the ring current of 250mA and the undulator gap of 200mm.
Radiation was confined and was absorbed by the lead shielding of the optical hutch. Moreover, the safety group placed radiation detectors inside the optical hutch and in the experimental hall nearby also, and that region was confined during the two commissioning days.
All the division of ALBA worked together to allow this first commissioning of M1, from accelerators operating the synchrotron and the front end, to the vacuum group, preparing the vacuum in the beamline and checking its status during the commissioning, engineering and infrastructure taking care of all mechanical elements and the cooling of the beamline, and computing preparing the equipment cabling, the protection system, the network and the remote control. The LOREA team constantly supervised the status of the beamline and analysed the images obtained by the fluorescent screen to investigate the performance of the beamline.
The project is co-funded by the European Regional Development Fund (ERDF) within the Framework of the ERDF Operative Programme of Catalonia 2014-2020.
