M. Schuh, M. Vretenar, G. DeMichele, S. Ramberger, R. Wegner, N. Alharbi

**DTL**

- measurements done with post couplers: measured tilde sensitivity,all gaps are in tolerance, aim: flat voltage
- to do measurements without post couplers: moving only tuners
- no exact Q measurements possible with actual setup
- water cooled end cups needed
- perform high power test (LINAC4 duty cycle) without post couplers at CERN: Measure X-Rays (action: contact safety staff), Kilpatrick, test with magnets in drifttube
- SPL duty cycle as 2nd priority due to heat problems with actual setup

**PIMS, thermal drifts**

- during operation with SPL duty cycle, PIMS modules will heat up considerably, the frequency will decrease of about 200kHz (worst case)
- if for any reason, one cell will get a small frequency offset, the power distribution within a PIMS module will change in a direction that will amplify this frequency offset and again the power distribution will change. Is this a drift (convergence) or an instability (divergence)?
- the strongest effect will occur for a frequency offset in one end cell. So assuming an initial frequency offset of kHz in one end cell,
- the power in this cell will fall down to of the nominal power level (more power will be dissipated in the other cells, the total power level is assumed to be constant all the time)
- as the power of the end cell is reduced, it cools, shrinks and its frequency increases further, in numbers, to kHz
- again the power drops, to and the frequency increases to kHz
- after the nth iteration, the frequency offset will be with in the case of the PIMS hot prototype
- as q<1, we have convergence and the final frequency offset is
- curves show the relation between the initial frequency offset and the final frequency offset for each of the 7 PIMS cells. Furthermore, the Tilt sensitivity and max-min/mean voltage errors including the discussed drift effects are given for frequency offsets in each cell. (RolfWegner)

-- MarcelSchuh - 17 Nov 2008

Topic revision: r2 - 2008-11-18 - MarcelSchuh