SRF2011 - List of Authors (Turlington, L.)

Paper

Title

Page

Fabrication, Tuning, Treatment and Testing of Two 3.5 Cell Photo-Injector Cavities for the ELBE Linac

405

A. Arnold, P. Murcek, J. Teichert, R. Xiang
HZDR, Dresden, Germany
G.V. Eremeev, P. Kneisel, M. Stirbet, L. Turlington
JLAB, Newport News, Virginia, USA

As part of a CRADA (Cooperative Research and Development Agreement) between Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Thomas Jefferson Lab National Accelerator Facility (TJNAF) we have fabricated and tested two 1.3 GHz 3.5 cell photo-injector cavities from polycrystalline RRR niobium and large grain RRR niobium, respectively. The cavity with the better performance will replace the presently used injector cavity in the ELBE linac*. The cavities have been fabricated and pre-tuned at TJNAF, while the more sophisticated final field tuning, the adjustment of the external couplings and the field profile measurement of transverse electric modes for RF focusing** was done at HZDR. The following standard surface treatment and the vertical test was carried out at TJNAF’s production facilities. A major challenge turned out to be the rinsing of the cathode cell, which has small opening (Ø10mm) to receive the cathode stalk. Another unexpected problem encountered after etching, since large visible defects appeared in the least accessible cathode cell. This contribution reports about our experiences, initial results and the on-going diagnostic work to understand and fix the problems.
* J. Teichert, et al., Proc. FEL 2010, Malmoe, Sweden, p. 453.
** V. Volkov, D. Janssen, Phys. Rev. ST Accel. Beams 11, 061302 (2008).

Poster TUPO019 [1.211 MB]

THPO016

Preliminary Results on the Laser Heating Investigation of Hotspots in a Large-Grain Nb Cavity

745

G. Ciovati, C. Baldwin, G. Cheng, R. J. Flood, K. Jordan, P. Kneisel, M.L. Morrone, L. Turlington, K.M. Wilson, S. Zhang
JLAB, Newport News, Virginia, USA
S. M. Anlage
UMD, College Park, Maryland, USA
A.V. Gurevich
Old Dominion University, Norfolk, Virginia, USA
G. Nemes
Astigmat, Santa Clara, USA

Magnetic vortices pinned near the inner surface of SRF Nb cavities are a possible source of RF hotspots, frequently observed by temperature mapping of the cavities outer surface at RF surface magnetic fields of about 100 mT. Theoretically, we expect that the thermal gradient provided by a 10 W green laser shining on the inner cavity surface at the RF hotspot locations can move pinned vortices to different pinning locations. The experimental apparatus to send the beam onto the inner surface of a photoinjector-type large-grain Nb cavity is described. Preliminary results on the changes in thermal maps observed after applying the laser heating are also reported.

Poster THPO016 [0.983 MB]

Paper	Title	Page
TUPO019	Fabrication, Tuning, Treatment and Testing of Two 3.5 Cell Photo-Injector Cavities for the ELBE Linac	405
	A. Arnold, P. Murcek, J. Teichert, R. Xiang HZDR, Dresden, Germany G.V. Eremeev, P. Kneisel, M. Stirbet, L. Turlington JLAB, Newport News, Virginia, USA
	As part of a CRADA (Cooperative Research and Development Agreement) between Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Thomas Jefferson Lab National Accelerator Facility (TJNAF) we have fabricated and tested two 1.3 GHz 3.5 cell photo-injector cavities from polycrystalline RRR niobium and large grain RRR niobium, respectively. The cavity with the better performance will replace the presently used injector cavity in the ELBE linac. The cavities have been fabricated and pre-tuned at TJNAF, while the more sophisticated final field tuning, the adjustment of the external couplings and the field profile measurement of transverse electric modes for RF focusing* was done at HZDR. The following standard surface treatment and the vertical test was carried out at TJNAF’s production facilities. A major challenge turned out to be the rinsing of the cathode cell, which has small opening (Ø10mm) to receive the cathode stalk. Another unexpected problem encountered after etching, since large visible defects appeared in the least accessible cathode cell. This contribution reports about our experiences, initial results and the on-going diagnostic work to understand and fix the problems. * J. Teichert, et al., Proc. FEL 2010, Malmoe, Sweden, p. 453. ** V. Volkov, D. Janssen, Phys. Rev. ST Accel. Beams 11, 061302 (2008).
	Poster TUPO019 [1.211 MB]

THPO016	Preliminary Results on the Laser Heating Investigation of Hotspots in a Large-Grain Nb Cavity	745
	G. Ciovati, C. Baldwin, G. Cheng, R. J. Flood, K. Jordan, P. Kneisel, M.L. Morrone, L. Turlington, K.M. Wilson, S. Zhang JLAB, Newport News, Virginia, USA S. M. Anlage UMD, College Park, Maryland, USA A.V. Gurevich Old Dominion University, Norfolk, Virginia, USA G. Nemes Astigmat, Santa Clara, USA
	Magnetic vortices pinned near the inner surface of SRF Nb cavities are a possible source of RF hotspots, frequently observed by temperature mapping of the cavities outer surface at RF surface magnetic fields of about 100 mT. Theoretically, we expect that the thermal gradient provided by a 10 W green laser shining on the inner cavity surface at the RF hotspot locations can move pinned vortices to different pinning locations. The experimental apparatus to send the beam onto the inner surface of a photoinjector-type large-grain Nb cavity is described. Preliminary results on the changes in thermal maps observed after applying the laser heating are also reported.
	Poster THPO016 [0.983 MB]