2. Linac4 status and perspectives
Alessandra Lombardi and Maurizio Vretenar for the LINAC4 team
Contents :
Linac4 commissioning up to 160 MeV;
Source;
Debuncher;
Reliability Run.
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

3. Made it to the final energy!
Safely on the dump.
It has been stripped.
It has been delivered
to the HST.
Oct 2013
3MeV 30 mA
Nov 2015
50 MeV 20 mA
Nov 2016
160 MeV 18mA
45 KeV
50 mA
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

4. Layout and commissioning stages
All items needed for the connection to the PSB are in house
LINAC4 machine layout- 352MHz
Pre-injector (9m)
DTL (19m)
CCDTL (25m)
Π-mode (23m)
3MeV
50 MeV
100 MeV
160 MeV
SOURCE
Plasma Generator
Extraction
e-Dump
LEBT
2 solenoids
Pre chopper
RFQ
CHOPPER LINE
11 EMQ
3 Cavities
2 Chopper units
In-line dump
3 Tanks
3 Klystrons : 5 MW
1 EMQ
114 PMQ
2 steerers
7 Modules
7 Klystrons : 7 MW
7 EMQ + 14 PMQ
7 steerers
12 Modules
8 Klystrons: 12MW
12 EMQ
12 steerer
Beam Commissioning stages
45 keV
3 MeV
12 MeV
105 MeV
Not yet the final source – details later
(50mA standalone)
(30mA-Nov15)*****
25mA – Nov16
October 2013
(10mA- Aug 14)
(30mA-oct 15)
(20mA-Nov15)
20 mA –Nov16
August 2014
(20mA – Nov15)
November 2015
(20mA – Nov 15)
18mA –Nov2016
June 2016
(20mA – Jun16)
October 2016
15mA – Nov 2016
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

5. Beam CURRENT 160 Mev matching and steering 3 MeV 45 keV
Source emittance
RFQ acceptance
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

6. Beam Current BCT Energy intensity L4L.BCT.1213 45keV 25 mA Emittance/
3 MeV
20 mA
RFQ Acceptance
L4L.BCT.4013
19mA
L4C.BCT.0717
50 MeV
16mA
Matching and
L4T.BCT.0107
160 MeV
14 mA
Steering
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

7. Reaching the final energy
Characteristic curves : energy out of an RF cavity as function of amplitude and phase.
Solid line : simulations,
Dotted : measurements
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

8. Reaching the final energy
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

9. Transverse measurements
From three (or more) profile measurements deduce the emittance. Technique refined in HSL by forward tracking and tomographic reconstruction.
At 160 MeV
X-X'
Emit [rms] = Pi.mm.mrad [ Norm. ]
Y-Y'
Emit [rms] = ]
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

10. Main parameters LINAC4 – CDR (2006) LIU specs march 2015
LINAC4 – achieved (IN PROGRESS)
Protons per bunch in 650 ns :
in 1.5 µm
70mA peak at the source
65 ma peak in the linac
40 mA after chopping
60 mA peak at the source
40 mA peak in the linac
26 mA after chopping
Injection over 20 turns
50mA peak
18 mA peak in the linac (30 mA potentially)
12 mA average after chopping (20 mA potentially)
Injection over 40 turns (ok for LHC beams)
160 MeV
0.4 π mm mrad
0.3 π mm mrad (at 160 MeV)
400 µsec 1Hz
Up to 600 µsec 1Hz
Fast Chopping at 3 MeV
2µsec inj kicker rise-time
Demonstrated , including transmitted beam quality
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

11. A word on the source Many improvement since march 2015 Intensity
Stability
Auto-Pilot (automatic regulation of critical source parameters for increased stability)
Caesiation with autopilot , time needed went from half day w/o beam to few hours in degraded beam conditions
Still needs attention
Control of the emittance
Optimised electrode shape
Matching into the LEBT
Mastering neutralisation?
Current at 3 MeV before chopping
Today’s LINAC4
20mA
Record LINAC4
( at 3 MeV)
30 mA
Nominal LIU
40 mA
Can be compensated with more injected turns in the PSB . Studies by Benedetto and Forte show that emittance is ok for LHC beams.
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

12. A word on the Debuncher
PIMS-like cavity located approx. 40 m after the last PIMS with the purpose of adapting the energy spread to the desired value in the PSB (from 120keV to 700keV rms). Note that the energy spread from the linac is about 300keV. Without energy painting the needed voltage is 900kV. Ok. With energy painting, the debuncher has to adapt to the velocity profile along the macro-bunch, i.e. more power is needed from the amplifier to dynamically change the phase. With the current amplifier the de-buncher cannot adapt to any energy painting scheme and a compromise on speed/energy spread/range of energy painting is necessary
and
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

13. Reliability Run
Purpose : insure a smooth transition from commissioning to operation, achieve a beam-avaliability (tbd) for the PSB as high as possible and possibly above 90%. (
Phase
When
0-Finalisation
Before May 17
Consolidation of LLRF and BI instrumentation.
CRUCIAL to respect the schedule
1-make the linac4 reliable by addressing weak points
June - August
Short runs followed by repairs/optimisation
Accelerator Fault Tracker in place; OP involved with Linac team still leading.
2-Mock-up of operation as after the connection
Sept- Mar18 (including 2 months shut-down)
Daily preparation of different beams, continuous operation for weeks, exploitation of the LINAC4 flexibility)
OP leading the run with linac team as support. Call-out list during working hours.
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

14. Reliability run – details
Keep in place HST dump , to have the possibility to have multiple destinations/users and verify the energy.
AFT + the expertise of the Aft team from the beginning (June 2017).
Beam-on time calculated from the logbook entries keeping into account that there is not a piquet service.
Software to facilitate running from the CCC should be transferred to OP or written by OP. needs have been identified.
Main dump
HST temporary dump
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

15. NEXT steps and planning
Achieve the HST goals
Achieve Reliability Run goals
Intervention, repairs : alignment, vacuum DTL, source (and new LEBT?)…..
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

16. Summary and conclusions
Construction and installation of LINAC4 finished at the end of 2016.
A beam of 15mA at 160 MeV has been obtained at LINAC4, it has been stripped and delivered to the HST.
The Nov 2016 measurement campaign confirms that all the technical choices for the linac are solid and that there are no fundamental show-stoppers or drastic changes needed.
Further adjustments on the source and improvement of the matching/steering should allow to reach a minimal LIU LHC beam of 30mA (vs 40 nominal).
The reliability run is the focus for 2017 and it is an important step in the transition to operation.
LHC Performance Workshop January 2017
Linac4 status and perspectives Alessandra Lombardi

17. LHC Performance Workshop 23-26 January 2017