Dmitry Gudkov Phase correction of the CLIC TBM in CLEX Dmitry Gudkov Wilfrid Farabolini

Dmitry Gudkov Contents Problem description Confirmation of the problem existence Possible solutions Ongoing and future actions

Dmitry Gudkov Problem description The problem was presented by Wilfrid during the CLIC meeting on 16-Dec-2014 Slides by W. Farabolini:

Dmitry Gudkov Confirmation of the problem existence The feasibility of a phase ~ 180 o shift have been investigated using the existing waveguide network (not installed on the TBM): -2 ports network analyser (Agilent) is used -Sij parameters at the GHz frequency are measured Output 1Output 2 S12 phase [ o ] S12 amplitude [dB] S11 [dB]-35.8 S22 [dB] The phase difference between the hybrid output 1 and output 2 is 91.8 o

Dmitry Gudkov Confirmation of the problem existence Distance between the input of the first AS and second AS in the SAS is which corresponds to 9 and ¾ (9.75) times the bunch spacing at GHz free space wavelength (25 mm); The RF phase at the second structure input must be -270 deg. or + 90 o from the RF phase at the first structure input; To obtain this phase the output #1 of the hybrid coupler must feed the 2 nd structure; However in the current installation the hybrid is turned and the output #1 feeds the 1 st structure.

Dmitry Gudkov Possible solutions Solution 1: Squeezing waveguide dimensions Attempt to obtain a phase shift of 180 o by squeezing existing piece of the waveguide network; The test was performed on the H-bent waveguide Result: The expected phase shift is accompanied by a large increase of the S11 and S22 reflections (- 17 dB for a phase shift of 56 o ): Evolution of phase shift (blue) and reflection (red) during waveguide squeezing It is not likely to fulfil the required 180 o phase shift; Method can be used for final phase adjustment on a range of 15 o approximately.

Dmitry Gudkov Possible solutions Solution 2: Additional waveguide segment for phase compensation Bending of distribution waveguides to allow spacer insertion; Spacer manufacturing and installation. Result: Sij parameters remain very acceptable: Preliminary bending was performed: deformedOutput 1Output 2 S12 phase [deg] S21 [dB] S11 [dB] S22 [dB] non-deformedOutput 1Output 2 S12 phase [deg] S21 [dB] S11 [dB] S22 [dB] The phase shift due to the deformation is minor (about 1 deg). 2 outputs of this non-deformed waveguide have a difference of phase of 17 deg. Such a difference of phase can be fixed by squeezing the waveguide.

Dmitry Gudkov Ongoing and future actions 1. Spacers design and manufacturing: Spacer Type 1: Copper part, works as big gasket Spacer Type 2: 2-sided CLIC RF vacuum flange 2. Accurate phase control will require many RF network measures during the installation and can be achieved by a limited squeeze of the waveguide and/or by flange torque control.