Impedance of current TCP compared to new TCP with button

New TCPP Problem with heating of one TCP in 2012  removed Collimation team decided to profit from an option in the existing contract to build one new spare, and proposed to insert BPM in TCP.  OK for impedance team? Need a recommendation Context: new TCTP design was not recommended to be extended to other collimators and below a certain gap due to the increase of tapering angle from 11 degrees to 16.5 degrees.  However, primary collimators have a special jaw with a 10-degree-taper close to the beam.  maybe not as critical as for other collimators since the modified tapering would be in the shadow of this tapering angle and further away from the beam.

Current TCP Current design New design 1194 mm 600 mm 10 degrees 11 degrees 68.5 mm

New design (proposal)

Jaw for new TCP with buttons  in fact smaller first angle 6.34 degrees compared to 11 degrees for phase 1

Reminder: TCTP and TCSP

New design (proposal) Similar impedance between current design and new design

New design (proposal) Similar impedance between current design and new design

Conclusion from BPM tapering Could be accepted, no special issue at first sight. Now, what about ferrite and RF contacts?

Should we close the gap?

Arguments Closing the gap suppresses modes, while ferrites try to damp them (see LRFF working group conclusions). Ferrites have an optimal frequency range of operation Ferrites can heavily suffer from beam induced heating RF contacts may lose contact (in this design with BPM there are long contacts that are more challenging) Serious problems encountered both with ferrites and non- conforming RF contacts in the machine Argument not related to impedance Ferrites can cause outgassing and can break easily RF contacts can cause UFOs

Proposed recommendation With the information we have, we would recommend RF contacts and reiterate the RF contacts design if necessary for reliability reasons. Is it possible to devise a redundant solution? (e.g. with ferrite behind the RF contacts) If possible, we could reinvestigate hybrid options (RF contacts everywhere except where long contacts are needed, and keep the possibility to install a few ferrites).

New idea to collect dust… Nice resonating plates!