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New Linac4 Plan for 2013/2016

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Linac4 Project Meeting 12 July 2012

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New plan – boundary conditions

Goal: Minimise the effort from support groups during LS1, in particular those that indicated problems during LS1 Day → survey, with a lesser extent CV and vacuum. Note that cabling (bottleneck for LS1) is not particularly concerned, the L4 cabling is being done in 2012.

Consequences:1. Availability of H- one year later (end 2016, after reliability

run → for connection to PSB from end 2017 (start of LS2), one year to fix remaining problems before connection.

2. Availability of 50 MeV protons delayed too (see next slides). Need to minimise:• Impact on the team (keep a constant interesting program)• Risks because of late discovery of problemsStrategy:1. Only 3 MeV beam tests in 2013 (on Test Stand first and then at Linac4

from September - no cooling water at Test Stand from end of June)2. Slow ramp up of energy to 50 MeV in 1st half of 20143. Faster ramp up of energy after June 2014.

No installations in 2013, slower installation in 2014, but need to complete the assembly of RF structures in the surface hall (cannot leave hundreds of small components exposed to air and dust for more than 1 year)

Cabling in Linac4 tunnel – 16.5.12

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Linac4 Masterplan

Ready for 50 MeV protons as

backup to Linac2

Ready for H-

Revised 2012/16 Masterplan, approved by the LMC on 27.6.2012

Connection of Linac4 to the PS Booster during LS2 (2017/18)

Start high-energy commissioning (12

MeV)

1 year reliability

run

End high-energy

commissioning (160 MeV)

Proposed new plan – LS1 details4

LS1

After LS1 (July-Dec 2014):Closing line for protons Commissioning to 100MeV

Note that the 2014 plan can be modulated depending on the actual situation with LS1

2014:Commissioning DTL1 (12 MeV)Commisioning DTL2&3 (50 MeV)

2013:3 MeV testsClosing RF structures

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Impact on support groups

Meeting with Survey on 26.6: the new plan reduces by about one half the required manpower and allows to recuperate 1 FTE for other activities → ok.

CV: only minimum services required in the tunnel during 2013 (ventilation, cooling for ion source, cooling for 3 MeV from August) → details being defined, seems no problem.

Vacuum: keeps activity on RF structures (outside of tunnel) but there is only minimum activity in the tunnel;

EN/EL Cabling: only local cabling required (from the cables already pulled) for 4 klystrons/modulators and 4 RF cavities.

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New Masterplan – a few comments

It is important that this Plan has been officially approved (in the Minutes of 27.6 LMC); it requires some fine tuning (and one of the goals of today’s meeting is to collect your comments and suggestions for an improved version) but the key points are fixed;

In particular, we need to see how moving the start of LS1 to 11.2.2013 impacts the plans of support groups (a meeting with SU is foreseen on 23.7) for the final trimming of the plan (but changes will be in the 1-2 month range);

The situation is not too bad: we get some more time for a complete testing of the 3 MeV part, then we go fast through the commissioning up to 100 (or 105?) MeV and then we get some more time for the completion of the PIMS and the commissioning to 160 MeV. We have lengthened the beam commissioning, meaning that we will hopefully work on only one shift instead of two and we take more time to think...

An (unfortunate) consequence of the new plan is that it rules out the option of having an LS1.5 intermediate length shut-down for the connection of Linac4. However, our goal remains to be ready for reliable delivery of a nominal H- beam to PSB at end 2016... and then we will se what happens. The recent experiences have demonstrated that medium and long-term planning are particularly difficult at CERN (connection of Linac4 during LS1 with start of PSB end 2014 was refused on the basis that the start of LS1 could not be delayed by 3 months and that the injectors had to run in 2014...).

The option of making 50 MeV protons with Linac4 remains open (see next slides).

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A new look at the proton issue

Some new elements in the analysis of 50 MeV proton production with Linac4 as Linac2 backup:

The results presented at Chamonix 2012 were preliminary. New informations are that

1. A recent paper (23.5.2012) indicates a slightly more encouraging figure (75% brightness) from simulations of proton injection from Linac4 (40 mA nominal beam)

2. By rearranging the klystrons (if needed) and reducing the margin for LLRF, the RF can allow increasing the current above nominal (only for emergency proton operation)

CERN-ATS-Note-2012-047: simulated PSB brightness with Linac4 nominal beam is 75% that of Linac2; Increasing Linac4 current to >50 mA looks possible with present hardware → can give the missing 25% to achieve

the same brightness in the PSB. More simulations are required to demonstrate that the PSB can accept the increase in Linac4 current.

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Work to do to explore the proton issue…

The option of injecting in the PSB 50 MeV protons from Linac4 looks more encouraging, the goal is to provide the same brightness for LHC as with Linac2 (but the high-intensity users will certainly suffer).

However, more studies and measurements are needed:- Simulations of injection of higher currents from Linac4 into the PSB;- More understanding of the PSB simulations (counterintuitive behaviour with space charge...);- Analysis of the maximum beam current allowed in DTL tanks 2 and 3 (2.2 MW for cavity and 53 mA

beam loading against 2.8 MW peak klystron power – no problem for LLRF compensation, could leave space for higher beam current – proton compensation is easier than with normal H- operation);

- Measurements of actual Q-values of DTL tanks (summer 2013). Assumed values have a good safety margin, could reserve good surprises...

If we decide to keep the 50 MeV proton option, some hardware is needed to close the vacuum chamber between the Linac4 DTL and the connection point at LT.BHZ20 (including appropriate focusing and diagnostics) and to shield the Linac2 area from the Linac4 proton beam:

- Design office and construction of temporary vacuum chambers and quadrupole supports in the position of missing Linac4 elements (→ with associated cost!).

- Shielding calculations for additional shielding (quickly added/removed).

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Why we could need the protons

Vacuum team worried for lifetime of the Linac2 sputter ion pumps (see IEFC 25.5.2012).

There is a high probability that we have to break Linac2 vacuum before LS2 to exchange the ion pumps (P. Chiggiato, private communication after LS1 day), and there is a high risk of leaks developing in Linac2 following this intervention.

If it is confirmed that the PSB can achieve a comparable brightness with 50 MeV protons from Linac4 as from Linac2, a possible strategy would be:

1. The intervention on Linac2 vacuum is done at the beginning of a winter shut-down; Linac4 would be already prepared for protons before (for shorter connection time);

2. If there are problems to re-establish the vacuum in Linac2, the connection of Linac4 to the line could be done in 1 month (instead of 2 without preparation), including shielding and possibly a temporary wall of concrete blocks (<1m thick?) to separate Linac2 from transfer line;

3. PSB would restart (on time!) with Linac4 as injector; the exchange could be transparent for the LHC, but for high-intensity users beam intensity will certainly be lower;

4. Behind the shielding wall, the repair of Linac2 can progress during operation. If successfully repaired, switching back to Linac2 could be done in a few days; if not repairable, operation has to continue with Linac4.

Temporary connection L4 for 50 MeV protons

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1. Missing PIMS cavities replaced by vacuum pipes and quadrupoles

on special supports

2. Transfer line completed

3. Small shielding

« château » installed (bricks)

4. No additional shielding towards

Linac2 Hall (only 50 MeV, hall becomes

no access area)

5. Open access door from inflector zone (now closed with

bricks)6. Temporary shielding with concrete blocks (1m ?) at the position

of L2 debuncher

7. Access to Linac2 zone for repair of tanks is

possible (but confined zone from the new access door)

Reversible:When L2 repaired, remove temporary shielding at end of L2, reinstall debuncher and reconnect BHZ20 to Linac2. The « château » can remain, as soon as the door to the inflector remains open.

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My last slide at LMC

Looking from the beam hole of CCDTL module 2 - Novosibirsk, 19.6.2012

The Linac4 project started in 2008, with the goal of completing in 2013. This was of course overoptimistic, and the date moved to 2014. Then (last year)

to 2015, and now to 2016... Slowing Linac4 is always an easy way to get resources, but:- Linacs are not easy machines. When they work, they work steadily and reliably

(the acceleration law is frozen forever in the metal...) but when they don’t work they are not easy to fix (examples: Linac2 vacuum, Linac4 H- source, ...).

- In particular, Linac4 will be:o the first linac in the world to use a fast choppero the first linac in the world to use CCDTL and PIMS accelerating structures o a linac with unique requirements to the ion sourceo a machine with sophisticated RF distribution and LLRF, new at CERNo a machine that from day 1 is required to have an extremely high reliability.

The basic layout is solid and conservative, but Linac4 is full of innovations that can need time to be tuned.

In theory, nothing changes for Linac4: connection was for LS2 before, and it for LS2 now... but we will see the full energy one year later and we will have one year less to address potential problems.

In conclusion, it is important to keep in mind that every delay in Linac4, including this one:1. Increases the risks for the project because of late discovery of problems;2. Increases the risks for the project because of retirement/departure of critical people;3. Increases the integral of resources required to complete the project (M and P).