JLAB, Newport News, Virginia, USA
We have fabricated two single cell 650 MHz cavities of a JLab design [1], for possible project X application. Both cavities were manufactured at Jlab from RRR>250 niobium sheet of 4 mm thickness using standard techniques such as deep drawing, EBW, BCP , hydrogen degassing heat treatment, high pressure ultrapure water rinsing and clean room assembly. A detailed description of the design and fabrication procedures is forthcoming [2]. Initially cavity #1 was – after final surface treatment by bcp – measured without any provisions for stiffening . As expected, the pressure sensitivity and the Lorentz Force detuning coefficients were quite high; however, the RF performance was very encouraging: the cavity exhibited a Q-value > 1011 at 1.6K, corresponding to a residual resistance of < 1.5 nOhm The initial gradient was limited to Eacc ~ 18 MV/m, limited by field emission. In a subsequent test, we are re-rinsing the cavity and are making provisions for stiffening up the cavity. By the time of this writing, this test is in progress; the results will be reported at this conference as well as results from the second cavity.
[1] F. Marhauser, JLab-TN-10-043
[2] F. Marhauser et al; IPAC 2011 to be published
JLAB, Newport News, Virginia, USA
80 new 7-cell, LL cell-shaped cavities are required for the CEBAF 12 GeV Upgrade project. In addition to ten pre-production units fabricated at JLab, the full set of commercially-produced cavities have been delivered. An efficient processing routine, which includes a controlled 30 micron EP, has been established to transform these cavities into qualified 8-cavity strings. This work began in 2010 and will run through the end of 2011. The realized cavity performance consistently exceeds project requirements and also the maximum useful gradient in CEBAF: 25 MV/m. We will describe the cavity processing and preparation protocols and summarize test results obtained to date.
