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GF SPS-POP meeting

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People present (in random order)
W. Krasny, W. Hofle, S. Evrard, G. Arduini, G Mazzola, P. Kruyt, D. Gamba, B. Marsh, T. Argyropoulos, F. Roncarolo, W. Placzek, F. Galleazi, J. Bieron, A. Martens.

. A. Martens opens the meeting with some news. TI18 visit happened on the 14th of November, E. Granados will report on it. CERN site acceptance test occurred on the 2nd and 3rd of November. Laser oscillator shipped to IJCLab and arrived on the 13th of November. Tsinghua University PhD student (Xinyi Lu) will visit IJCLab for 6 months and conduct a power test experiment with this laser, R&D amplifier, and new R&D mirrors. Last but not least, Witek is back to work, after knee surgery and difficult recovery.

. E. Granados reports on the laser site acceptance tests. The list of performed test had been listed. It took 5-10min to set up the laser, that is found to be turn key and easy to start. RMS intensity stability is found of 0.085% after warm up over a 8h overnight test. The tunability of the oscillator frequency has been verified. A 7.2kHz range is obtained (slope 0.072088 kHz/V). Laser power and optical bandwidth is stable with change of piezo voltages. Beam profile is found Gaussian with 1.17mm diameter (at 86.5%). The pulse duration is found of 190fs (hyperbolic secant fit). Output spectrum is found to be entered at 1031.8n and bandwidth of 7nm. In conclusion the supply performs according to the specification.
W. Hofle asked if tests of the laser have been performed by modulating the piezo voltage with sine excitations. EG answers it has not been done. AM further add that the lock on the R&D optical cavity will provide an indirect answer to that question.
G. Arudini asks why the power meter qualification is made with a 1064nm powermeter. EG answer that it is a setting on a old pwoermeter, but setting it to 1031nm would not change the measurement results by more than 1%. The sensor used is a made by a heat measurement, photon at 1030 or 1064nm behave in very similar manner on that respect. The RF measurement for phase noise performed at CERN was not consistent with that measured at Factory. Another measurement will be made at IJCLab with optical beating. 
GA remarks that the frequency depends on pressure and asks if it could be a problem for the operation in TI18. Discussion with EG and AM and SE concludes that a measurement in the TI18 frequency change. It is suggested to make a measurement of pressure in the TI18. AM confirms that the biggest worry would be to have a sudden, large, change in pressure that could delock the laser and cavity.

. E. Granados reports on the TI18 access. Door was closed for several years. Fire brigade inspection happened first with Oxygen sensors. No GSM after few meters inside tunnel. Normal level of oxygen and CO2 there. FFP2 mask are recommended due to a possible level of amiante in the tunnel. EG show a video. No humidity found, not so much dust. No dead animals or other sign of contamination found. 3D scan has been made. BatMons were installed at the laser output, currently blocked by a panel. All foreseen activity were done. GA asks if the laser will be installed in the shown region where the BatMons will be installed. EG confirms. The eight for the penetration is about 70cm which is ideal for the laser transport line.

. GA mention that Xenon is foreseen for ALICE operations. GA asks if we have informations about cooling performance of Xe. WK answers that we likely ned to lower the ion's boost to cool down We in the SPS. A detailed check on on to cool down Xe ions is welcome. WK agrees on that respect. In particular Xe beam lifetime is also a matter to investigate.

. WK also reports on other broader aspects of Gamma Factory. Wk discusses with Atomic Physics colleagues to understand what happens when there is additional external B field (~1T) at the location of the Fabry Perot Cavity. The resonance frequency could be tuned using this external field. Interplay of Zeeman and Stark effect could allow to measure more precisely the beam energy. 11th of December, visit of Catania and Frascati groups to discuss their implication to the Proof of Principle. These people are interested in measurement, characterisation of photon beam. Presentation at ISOLDE meeting will be done, and a Gamma Factory will be presented at a workshop at Bern about Dark matter searches. 
GA asks about if there is further discussions with NTOF and ISOLDE. WK answers that indeed, discussions will continue with ISOLDE during an upcoming meeting. Catania people are involved in NTOF, so further interaction will happen in December. D. Alesini is interested in abundant production of neutron for reactors. Further discussion occur on the effect of external B field in the Fabry Perot on cooling with WK, DG and GA.

. A Martens asks if someone has something to mention. Nobody replies. Meeting is closed.

 

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