27 July 2006
Building and Testing a String of Cryomodules - a Task for S2
An ambitious and crucial goal of the ILC R&D programme is to build and test a string of superconducting RF cryomodules that operate at or near the design gradient. Achieving such a milestone would help optimise the design and minimise the risks for full-scale production of the ILC main linac. Large and long-term R&D programmes aimed at this goal are getting underway at several of our laboratories. The GDE R&D Board has recognised the need for the GDE to provide guidance to these programmes - therefore it is forming a special task force called S2 that will be co-chaired by Hasan Padamsee (Cornell) and Tom Himel (SLAC).
This new task force is complementary to the one I described in my last Corner: the S0/S1 task force led by Lutz Lilje (DESY). S0/S1 coordinates the programme that is supposed to demonstrate the ILC accelerating gradient. Lutz' group is focusing on understanding the details of fabrication and processing required to reliably achieve the baseline cavity gradients of 35 MV/m- They are also developing a plan for demonstrations with single cryomodules. Once those goals are achieved, string tests will start in the labs.
The basic building block of the ILC main linac consists of an RF Unit with three cryomodules. The desired string for the ILC R&D plan will be made up of many RF units, each with full RF power, controlled substantially as in the final linac. An important question will be how many modules are needed and whether this is enough to become a first important step towards industrialisation. The S2 task force will define the detailed goals and milestones of this programme, along with a timeline for its realisation. Some of the crucial specifications of the string have been defined in the R2 ranking of R&D issues in the TRC report (2003).
We are just in the process of forming the S2 task force the formal charge and full membership are not yet decided. One other important additional question for this group to address is whether there should be a test linac to inject beam into the string, and if so, what the functions of the string, the operation of the string in realistic conditions, and the use of a test linac as a facility for beam measurements should be.
-- Barry Barish