Linac R&D Update May 15, 2006

L-Band Source Consists of a LLRF system (VME/Epics based), a SNS High Voltage Converter Modulator (on loan), a Thales 2104C 5 MW klystron, a 5 MW isolator (from SPA Ferrite) and pressurized (30 psig N2, no SF6) waveguide that feed two experimental areas (one in the NLCTA enclosure that will power an ILC prototype positron capture cavity, and one for a coupler test stand). Source currently configured with a Thales 2104U klystron and the waveguide terminated in a load just after the isolator. –Expect to receive the TH2104C klystron on May 27.

Lead Box Containing Klystron Pressurized WG Load Isolator Current RF source layout with power terminated in a nearby load

L-Band Source (cont) Have operated the system to produce 3.3 MW, 1 msec rf pulses at 5 Hz. System processed quickly although had several arc-monitor faults. Discovered arcing on some of the flange surfaces – found the flange faces were not flat (5-10 mils) – also had properly tighten them. –Have since learned much more about flanges from industry, DESY, KEK and FNAL, not all of which is consistent –For next test, have machined flat the flanges to 1 mil. Will try both metal-to-metal and metal-metal gasket-metal transitions. Have since upgraded SNS modulator using parts provided by Bill Reass at LANL. In process of testing it with water and resistor loads

SNS HVCM Modulator

Resistive Load and TH2104U Klystron

Waveguide Distribution Coupler Test Stand Capture Cavity RF Switch

Positron Capture Cavity Half cell parts complete for body Need to braze pairs, do a second machining and then tune – expect to do in 6 weeks First windows available for test in 7 weeks Full cavity done in about 3 months (mid-August). Still low shop priority as LCLS submits rf work for gun. Recently completed installation drawings for NLCTA. Also Boeing donation of solenoid approved – need to arrange shipment to SLAC.

ILC Positron Capture Cavity Prototype

As Installed in NLCTA w/o Window

Coupler Development Have decided on basic plan to test coupler parts. Setup uses a detachable center conductor and 20 inch long test sections Chris N and Gordon working on rf and mechanical design

Design of WG-to-Coax Adaptor

Multipacting Simulation of TTF3 Coupler Bellows Primaries -Green, Secondaries- Red “Cold Side”

SC Quad/BPM Status Magnet received from DESY in January after initial testing there in a vertical Dewar. Gas-filled leads received in March. With help of Tom Nicol at FNAL, developed a low heat loss, stable support design for the He vessel. May adopt similar support structure for the ILC linac. Cryostat currently being built in SLAC shops and magnet / quench system being configured. Had discussion with Bldg 25 managers as to the logistics to install He transfer lines (safety review planned). Consider accelerometers to buy to vibrations tests. First tests of new magnet measuring coil planned during the next month using a NC quad. SC quad measurements planned for August. BPM triplet built, installed on girder in ESA and operated during run that started on April 24.

Cryostat and Cryogenic System

BPM Triplet Results from Recent Run (0.8 micron resolution, 1.4e10 electrons, Q of 500 for clean bunch separation)