Minutes of the CCinS working group

3^rd meeting on Friday 04/12/2009 (11h00, 6/2/004)

Present: Rama Calaga (RC), Nicolas Delruelle (ND), Nicolas Gilbert (NG), Elias Metral (EM), Joachim Tuckmantel (JT),  Giovanna Vandoni (GV).

Excused: Frank Zimmermann (FZ), due to a crash meeting for LHC (he finally came at the end of the meeting).

Absent: Olivier Brunner (OB), Jorg Wenninger (JW).

1)  Comments of the previous (2nd) meeting

 - EM wrote a cost "> 200-300 CHF", which ND wanted to correct to "> 300 CHF" (this has been modified in the minutes of the 2nd meeting).

2) Follow-up of the actions of the previous (2nd) meeting:

- NG, EM and GV went in the SPS tunnel on Tuesday 24/11/09 to have a closer look to the possible locations discussed in the previous meeting in LSS4 and LSS5. In particular we devoted quite some time around COLDEX, as it seems to be the best location at the moment (see all the photographs taken by NG at \\cern.ch\dfs\Users\n\ngilbert\Public\CCIS). GV took many info (which were reported during this meeting, see below). ND wanted to come but could not as he did not have the access rights. This was solved meanwhile and he could go down to look at the cryogenics equipments when there is an access.

- EM and RC met the following day to discuss the COLDEX possibility (with its bypass), some info received by Rama from KEK and the possible measurements in the SPS.

- In particular, it seems that the total width (from beam centre to the outer dimension) is 725 mm, which is much bigger than the limit of 580 mm for an installation in the tunnel => It cannot be in the tunnel and has to be in a cavern, as COLDEX.

- From the info RC got from KEK, the static heat load is 15 W (He at 4.4 K) and the dynamic one (i.e. with full RF) is 50 W (corresponding to Vkick = 1.5 MV). This leads to a total power of 65 W. Therefore, with the refrigerator available in COLDEX of 100 W, it should be OK, which was confirmed by ND. RC stressed that some Nitrogen cooling is also needed (110 W for liquid N2 at 80 K) and JT mentioned that in this case this is much more critical, and this should be closely followed up (NG was informed).

- RC will make a presentation at the next meeting where he will summarize all the info he got from KEK and where he will present the possible measurements in the SPS, with some orders of magnitude (see Action 19).

- NG asked ND whether the big white tank on surface is still useful or if it can be removed. This is a tank of Nitrogen (azote) at the entrance of BA4. ND will follow this up as some tanks have to undergo some acoustic tests. This tank could be used if one wants to boost a little bit the cryogenics with some liquid Nitrogen.

- NG discussed with an ODH expert (G. Lindell) and the following question was raised : in case of incident like brutal vacuum break, what would be the He flow to be expected from the safety valve(s)? What is the outlet diameter of the existing safety valve(s)? For the rest, it seems that ODH would NOT be a major problem for CCinS. We noted together that COLDEX is installed in a small cavern. We should be prudent about possible He accumulation over there. So a dedicated He detection/alarm system would be envisaged (10 to 15 kCHF + cabling to surface).

- At the end of the meeting, FZ mentioned that he had some email exchanges with KEKB and he was informed that KEKB will run until June next year. Therefore, it will not be possible to recuperate the CC at the end of this year but next summer at the earliest.

3) GV's talk on the possible COLDEX removal:

- GV started with a short review of the history of COLDEX (it was designed in 1994). It is a modular, versatile test-bench, simulating an extended vacuum chamber at cold. It was operated with 20 000 l dewar or refrigerator.

- Recuperation for further studies (LHC related) is highly attractive, if not yet necessary.

- If CC is NOT installed in BA4, COLDEX should stay in place.

- Replacing COLDEX by a drift space would take approximately 3 weeks. It is known that it is possible to dismantle it and reinstall it as it was already done several times in EPA and SPS.

- Concerning the recuperation of some equipments, the refrigerator can be kept. The transfer lines have to be negociated with COLDEX owners, but ND said it will be better to build new ones as they are not so good. Finally, concerning the translation tables, the weight of COLDEX is 0.5 ton (to be compared with 5 tons for the CC). Furthermore, for height considerations it seems that we will not have the space to keep them.

- Due to the large dimensions of the CC (750 mm width), EM asked if it will still be possible to play the same trick with the Y-chamber? It seems yes as for instance NG remembered us that this is also used for the TED in the SPS (TBSM.11672). Can we still move 5 tons (as the weight is much larger than the one from COLDEX)? This mechanical problem, with the available space, has to be followed up.

- JT asked whether we have the good equipments to move the CC with its 5 tons.

- The next step of GV would be to make a detailed planning for the COLDEX removal. However, her analysis seems to be sufficient at this level of our study.

- Reminder: the vacuum chamber has a diameter of 159 mm (external) around COLDEX.

4) KEK drawings shown by Rama: 1, 2, 3 and 4

- The total length to be installed is 5.081 m.

- It seems that there will be only ~ 20 cm to install the rails, the motorization etc. which could seem to be tight, but NG reminded us that it is very similar for the SPS TBSM. To be followed up in detail. However, it could be that the KEKB cavity is too big to be installed in the SPS (the KEKB cavity is not ideal as there was already the issue of the frequency, but the advantage is that it will be available in few months). RC reminded us that there is a R&D program and that we could have a CC about 2 times smaller but not before ~ 3 years. RC will ask KEK if they can reduce the height by few cm.

- NG suggested that we contact the Survey People (e.g. Christophe Podevin) asap to have a precise idea of the whole area (see Action 20 below). This could be translated in a small mockup. According to NG, the Survey People would need ~ 1/2 day in the SPS.

- ND asked RC if some drawings of the cryogenics interfaces are available. RC will ask KEK.

- The volume of the vessel of He is 400 l (mixture of liquid and gas). It is more than the 50 l estimated before. Rama will ask KEK to have more details as it seems quite a large value. NG reminded us that if we have 400 l of liquid He at 4.4 K and this volume is liberated at atmospheric pressure and room temperature, the volume will be multiplied by ~ 700, leading to ~ 280000 l.

- NG asked RC if he could check what the safety around the KEKB CC is.

- NG asked which kind of electrical power is finally needed for the CC. JT answered that he made a follow-up for the klystrons and apparently the DESY people are afraid to detune one of them to 510 MHz, tune it back and use it then (they have a big one 800kWKlystronFromDESY(Philips) and a small one 250kWKlystronFromDESY(Thomson)). They propose us to buy the Thomson one (250 kW). JT discussed with Eric Montesinos who thinks it would be 'no problem' to buy (tubes) and buy/build (amplifier racks + housing) a transmitter with IOT * around 500 MHz (we order such for 800 MHz anyway and the lower frequency helps to get instead of 60 kW @ 800 MHz about 80 kW @ 500 MHz (Eric's educated guess). Such an amplifier could deliver up to 80 kW, but they could be combined in power of 2, i.e. 2 for 160 kW (or 4 for 320 kW). But it is not for free, about 400 kCHF per transmitter. Apparently 'all' light sources work at 500 MHz and use such amplifiers. To answer the question of NG, JT said that the electrical power needed for 1 IOT of 80 kW (in DC) is ~160 kW (i.e. the electrical power needed is ~ 2 times the RF power) at 400 V (AC, 3 phases). For 2 IOTs (to have 160 kW of RF power, which will cost 2 times 400 kCHF), an electrical power of ~ 320 kW is needed. JT said that he prefers Eric's solution to the DESY solution, as the DESY klystron will also not be cheap (need a power supply, retuning klystron, re-retuning for return, ...) and might remain a 'bricolage' with some problems.

* IOT = Inductive Output Tube. An IOT can be considered as a klystron/tetrode hybrid. It has advantages over the klystron in terms of linearity and efficiency and over the tetrode in gain and output power. IOTs have become an accepted technology in the commercial sector, notably as TV transmitter tubes. They are now beginning to see service in scientific applications. An example of this was given in an EPAC2006 paper for the Diamond Light Source (IOT testing at the ERLP), which was due to become operational in 2008. Diamond should use four 80 kW, 500 MHz IOTs for each superconducting RF cavity.

- ND said that concerning the cryogenics compressor, the electrical power requested is 120 kW at 400 V (AC, 3 phases). Adding the RF and cryogenics requests, an electrical power of ~ 320 + 120 = 440 kW is needed.

- NG asked RC if we need more physical space around the CC in the tunnel? If we need to change cables, we have to open the cryostat and it has to be done during shutdown time.

- NG mentioned that we might have a problem with the BusbarBox, which might need to be dismantled to install the crab cavity.

5) JT's talk on the speed of voltage changes in crab cavities:

- JT made a detailed analysis of the speed of voltage changes in crab cavities, a machine protection issue for both the LHC and the SPS. When a crab cavity gets out of control and changes its voltage/phase, the beam may also get out of control. If the speed of change is so fast that the beam dump system  requiring 3 turns (≈ 300 micros) in the worst case cannot react in time, severe machine damage is possible. Here, only the possible voltage/phase change scenarios is considered. The possible aftermath for the beam is not analyzed. JT gave 2 numerical examples at the end of his talk where quite huge transverse impedances are obtained for relatively small (unavoidable) offsests.

6) Actions to be taken for the next meeting

- Action 1 (from 1st meeting): JT will contact OB to discuss possibilities with klystrons (where can we found one as it seems KEK will not give us their klystron? Can we have the good frequency? If not, can we modify the frequency? By how much? etc.). DONE (in fact JT follows this as OB has no time).

- Action 2 (from 1st meeting): FZ&RC will contact KEK to check the figure of the speed for the dynamic tuning (1 kHz/s or 10 kHz/s?). DONE.

- Action 3 (from 1st meeting): FZ&RC will contact KEK to check the heat load (static + dynamic). DONE.

- Action 4 (from 1st meeting): ND will check which kind of refrigerators could be available (power capacity?, fixed or mobile? etc.). DONE.

- Action 5 (from 1st meeting): NG will start checking where 5 m of equipments could be installed (with a distance between beam and outside dimensions of ~ 0.5 - 1 m). DONE.

- Action 6 (from 1st meeting): EM (with NG and ND) will contact Miguel Jimenez and Giovanna Vandoni (Vacuum) to check what the status with the old experiment COLDEX in LSS4 is and see if we could remove it and install the crab cavity. In fact Giovanna could also make a summary at one of the next meetings. DONE.

- Action 7 (from 1st meeting): EM&NG&ND (and any other people) would like to go and visit LSS5 and LSS4 (in particular COLDEX) => NG will add us in the SPS access requests. We could do this access in case of SPS stop or after December 16th (i.e. on 17/12/09 or 18/12/09). DONE.

- Action 8 (from 1st meeting): RC will send all the crab cavity impedance data to Elias.

- Action 9 (from 1st meeting): RC&FZ will contact KEK to have a description of all the feedbacks used with a crab cavity operation. 

- Action 10 (from 1st meeting): EM will contact FC to check if the Schottky monitor can still be used. DONE. (still waiting for final answers by Thomas Bohl).

- Action 11 (from 1st meeting): RC&FZ will provide a detailed list of what we want to measure (precisely) and how, with (if possible) numbers and pictures without and with the effect of the crab cavity (for instance coming from KEK measurements) => RC will make a presentation at the 4th meeting.

- Action 12: RC&FZ will contact KEK to check which cavity (HER or LER) could come to CERN.

- Action13: ND will show some slides about the LSS4 cryogenics installation during the next (3rd) meeting => ND could not do it as he could not go in the SPS tunnel (no access rights).

- Action14: GV will make a presentation about the old COLDEX experiment (and the possibility to install a crab cavity instead) during the next (3rd) meeting. DONE.

- Action 15: ? will check the effect of the crab cavity detuning by simulation.

- Action 16: NG will check where we have ~ 1 MW of power available in the SPS.

- Action 17: JT will present his analyses of possible failures on few slides during the next (3rd) meeting. DONE.

- Action 18: NG will follow the ODH issue. For this, RC will contact KEK to have the total amount of He underground => Ongoing.

- Action 19: RC will make a presentation at the next (4th)  meeting where he will summarize all the info he got from KEK and where he will present the possible measurements in the SPS (with some orders of magnitude).

- Action 20: EM will contact the Survey People (e.g. Christophe Podevin) asap to have a precise idea of the whole area around COLDEX. This could be translated in a small mockup. According to NG, the Survey People would need ~ 1/2 day in the SPS. 

7)  Miscellaneous

- Next (4th) meeting on Thursday 10/12/09 between 14:00 and 16:00 (max), in room 6/2/004.

Minutes by E. Metral, 06/12/09