How CLIC-Zero can become less expensive

How CLIC-Zero can become less expensive Grudiev, D. Schulte 16/06/09

Cost of CLIC-Zero from Hans Half of the price is from DB modules (modulator+klystron+structure) Can we reduce the number?

DB injector current reduction • Increase DB injector bunch spacing by factor two keeping the same total number of bunches, what means DB accelerator pulse length will be factor two longer BUT the peak power is 2 times lower and so the number of modulator+klystron modules • To operate in full beam loading regime reducing current by 2 means reducing gradient by 2. Therefore if we want to use nominal accelerating structures we have to increase the number of the structures by 2. • One klystron + modulator will feed 4 structures instead of one • In order to arrive to the nominal final DB current one more combiner ring will be necessary. This could be the same as CR2 which means it can be reusable. It also can be placed in the same tunnel as CR2. • Since DB energy is lower than in CLIC incoherent synchrotron radiation effect on the energy spread between the bunches is smaller and doubling the time of combining the bunches should be still less than in CLIC.

Pros and cons • Pros • number of klystrons and modulators is reduced by 2 • Cons • this is not the nominal CLIC DB combination scheme but something more complicated (as usually) • number of accelerating structures increased by 2 • if the DB linac length is driven by the structure length, the length of the linac is increased by 2 as well • since one klystron feed 4 structures larger waveguide network is necessary • additional combiner ring is necessary, which could be the same as CR2 and in the same tunnel

On the choice of DB accelerator frequency Grudiev 16/06/09

motivation • There are indications that an optimum power per klystron is significantly lower than 33 MW assumed before (see Erk’spresentation at the last ACE-meeting, the following two slides are from there) • Can we re-adjust CLIC (or maybe just CLIC500GeV) parameters so that it is more easy demonstrate-able, for example: • Reduce sector length • Reduce DB current • Reduce DB energy • Can we profit from ILC rf power source developments ?

Cost per 100,000 operating hours and per MW • Even if this model may be wrong, there will be a cost per MW and per operating hour: With the above model, this becomes: • Blue: present state of the art • Red: assuming a major investment into the development of a dedicated 30 MW tube 4th CLIC Advisory Committee (CLIC-ACE)

Existing: ILC 1.3 GHz MBK’s (10MW, 1.5 ms, 10 Hz) • CPI: VKL-8301B (6 beam): 10.2 MW, 66.3 %, 49.3 dB gain • Thales: TH 1801 (7 beam): 10.1 MW, 63%, 48 dB gain • Toshiba: E3736 (6 beam): 10.4 MW, 66 %, 49 dB gain 2. 1. 3. 4th CLIC Advisory Committee (CLIC-ACE)

ILC - CLIC 10 MW, 5 Hz, 1.5 ms - the same average power as for CLIC3TeV: 10 MW, 50 Hz, 150 us • To summarize • Changing DB accelerator frequency is certainly a lot of work. But it is maybe not too late. • We also can use this (maybe the last before finalizing parameter choice for the CDR) opportunity to change CLIC DB parameters keeping in mind the “demonstrate-ability” of CLIC as it has been mentioned in the last ACE review. • The smaller a DB sector, the smaller the CLIC-Zero could be, or the closer it could be to the sector • Changing RF power source frequency to that of the ILC will create a new very big area of common interest. Not only klystrons but all rf components and subsystems. This will help to find resources and to facilitate further R&D on the klystron (peak power, efficiency, price, etc.) • All this even more important for CLIC-500GeV than for CLIC-3TeV since the DB will dominate even more the price of the collider and one have less time and resources for R&D

How CLIC-Zero can become less expensive