1. Alain FRANCE for the ESS RFQ Team at CEA Saclay
Accelerator/RFQ
Alain FRANCE
for the ESS RFQ Team at CEA Saclay
April 21, 2015

2. RFQ Overview Deliverables Planning
RFQ realized in 5 sections (L = 0.92 m); total length = 4.58 m
CuC2 copper and stainless flanges
38 vacuum ports (24 in S1-S2-S4-S4)
60 adjustable slug tuners (34 in S1-S2-S3-S4-S5), 80 mm dia.
8 end-tuning rods (4 per end plate)
8 10mm-diameter cooling channels per section (variable length)
2 power coupling loops (S3)
20 pickups for voltage profile reconstruction
Deliverables
tuned and conditionned RFQ on its support
RF distribution system
water cooling skid
Planning
January start RFQ machining
October start RFQ tuning
July ready at ESS

3. Schedule

4. RFQ Technical performances
L3 System Requirements and L4 RFQ EMR System Requirements, Dec 19, 2014 Ed.
Frequency
nominal MHz,
controllable over ±100 kHz with Df3dB/10 resolution during operation
Df3dB over 10 sec agility
Df3dB/10 stability during pulse
10 Df3dB separation of other modes
Power
dissipated 1.6 MW max with 70 mA beam current
4% duty cycle
reflection coefficient < 15 dB at nominal beam current
RF couplers sustend Inf SWR
Voltage
voltage profile satisfying beam dynamics requirements
1.9 Kp max E-field
quadrupole component error < 1% (TBC with beam dynamics analysis)
dipole components < 1% (TBC with beam dynamics analysis)
2 pick-ups min for LLRF (+20 for voltage profile monitoring)

5. RFQ Technical performances
Vacuum
pressure < mbar over 75% of RFQ length
Geometry
vane tip surface tolerance < 20 mm
transverse vane displacement < 30 mm wrt theoretical vane position
transverse vane tilt < 30 mm over 1 m
transverse section displacement < 30 mm wrt theoretical beam axis
transverse section tilt < 30 mm over 1 m
Temperature
warm-up < 30 minutes
avoid corrosion
+ water cooling system requirements under transfer from ESS to CEA
Status of design studies
 RF design of cavity completed; design of RF distribution in progress
 thermal-mechanical design of cavity during operation completed
 mechanical design (supporting, transport, handling, ...) in progress
 water cooling skid design in progress (interfaces)

6. RFQ Selected technologies
Deliverables
tuned and conditionned RFQ on its support, RF distribution system, water cooling skid
RF design
four-vane structure, naturally stable single segment
tunable devices: end rods, vacuum ports, slug tuners
Fabrication of RFQ modules
4 electrodes with modulations and apertures for ancillaries
one step of copper-copper brazing in vertical position (IPHI)
5 modules with length < 1 m in agreement with demonstrated technology
Brazed vacuum ports
avoid machining of grids in the vanes
accurately positioned after electromagnetic measurements, prior to braze (Linac4)
RF couplers
loops offer less power dissipation and voltage ripple (Spiral2)
small coaxial window
standard tuner port
allows coupling adjustment at final Q
Adjustable slug tuners
performances achieved at last tuning step are saved under vacuum
allow for last minute corrections, after transport for instance
no delay required for machining after last tuning step

7. RFQ Selected technologies
RF distribution
one magic Tee, one power load and two feeders
loops in opposite quadrants to minimize voltage perturbation
phasing trombone to minimize reflection coefficient
Voltage profile monitoring
5  4 pick-ups will allow reconstruction of voltage profile
check RFQ voltage integrity vs. time
voltage profile corrections are possible to some extent
Water cooling
dedicated skid with four independent circuits
independent control of frequency and voltage function
eventually useful for voltage corrections
(superseded view with hybrid)

8. RFQ Integration and Verification
 A cavity with 2 RF power loops + 1 vacuum port + 1 adjustable slug tuner
RF power loop
validation by manufacturing followed by conditionning with a new RF source at CEA
ESS RFQ loops separately conditionned: RFQ conditionning expected to be shorter
Adjustable slug tuners
performances achieved at last tuning step are saved
Carlo Rossi Review: "The proposed use of adjustable tuners is an interesting option to assure the possibility to tune the accelerating field after transport and installation in the ESS tunnel; in the case of Linac4, after transport into the tunnel, it has been calculated that a change of the tuner penetration of few tenth of mm would be required to re-establish an accelerating field within the specified range. It would be worth investigating the impact of such solution on the long-term reliability of the system, once a detailed design has been developed."
Validation of tuners and vacuum ports assembly process

9. RFQ Organization at partner lab

10. RFQ Budget and cost-book

11. RFQ Major Procurements
Call for tender summer 2015
Start manufacturing beginning of 2016
Assembly on support nd part of 2017
Conditionning and test with beam st part of 2018

12. RFQ Top risks Schedule will be run in parallel Interfaces
CDR remark: “On the other end the schedule shows that three months could be sufficient for the complete fabrication of one segment, which appears as a very optimistic estimate; the fabrication of segments appears in the schedule as a serial process, while in reality it should be possible to organize the construction such that some fabrication stages can progress in parallel. This aspect is a key point in the discussion with the companies that will participate to the tender, as well as the required logistics, which may have a considerable impact on cost and schedule.”
 start rapidly copper part manufacturing and define the equally important industrial process, machining process and brazing process
will be run in parallel
Interfaces
 We need to have more validated information about interfaces with building (floor and electrical power), utilities (RF and vacuum), linac (LEBT and MEBT)

13. Next Six Months Call for tender for RFQ manufacturing Copper delivery
Copper treatment by HIP technic
Coupler test bench manufacturing
CDR2 to clarify interfaces to finalize the RFQ support design (handling and installation)

14. RFQ Summary
 design activities (RF distribution, supporting, handling, water cooling) going on
 intensive exchange of interface informations
 realization technologies identified, supported by prototype cavity
 call for tender in summer 2015 for final delivery mid-2018