1. Andrea Pisent INFN Italy
Drift Tube Linac
Andrea Pisent
INFN Italy
April 21, 2015

2. Overview DTL design Production critical steps Critical interfaces
Istituto Nazionale di Fisica Nucleare (Italy)

3. Schedule
Istituto Nazionale di Fisica Nucleare (Italy)

4. Technical performances (SoW)
The DTL (Drift Tube Linac) cavity is constituted of 20 modules, assembled in 5 tanks, composed of 4modules each, for a total length of approximately 40 m.
This profile describes the life cycle phases of the DTL regardless of the responsibilities assigned to contributors of this Scope of Works.
DTL design
Manufacturing and test of components
Assembly, low power test and tuning of each tank.
Transport and Installation in the ESS tunnel in Lund
Check out and RF conditioning to full power
Beam commissioning in two steps, beam dump after tank 1 and tank 5
Operation with the other Accelerator components (and neutron production target).
This scope of work describes the points from 1. to 6.
First tank
CERN-INFN prototype
Istituto Nazionale di Fisica Nucleare (Italy)

5. DTL Input Constraints (after the design update in 2013)
Requirement
Target value
Comment
Particle type H+
H- are possible
Input energy
3.62 MeV
+- 50 keV
Output energy
90 MeV
Input current
62.5 mA
Peak, (2.86 ms long with a repetition rate of 14 Hz)
Input emittance
0.28 mm mrad
Transverse RMS normalized
0.15 deg MeV
Longitudinal RMS
Emittance increase in the DTL
<10%
Design
Beam losses
<1 W/m
Above 30 MeV
RF frequency
MHz
Duty cycle
<6%
Peak surface field
<29 MV/m
1.6 Ekp
RF power per tank
<2.2 MW
Peak, dissipated+beam load, including
Module length
<2 m
Design constraint
Focusing structure
FODO
Empty tubes for Electro Magnetic Dipoles (EMDs) and Beam Position Monitors (BPMs) to implement beam corrective schemes
PMQ field
<62 T/m
Lund _12_02 Audit

6. Beam dynamics Uniform input distribution ∆𝜀 𝑥,𝑦 =2%, ∆𝜀 𝑧 =1%
Max Gradient ~61.6 T/m FODO lattice
∆𝜀 𝑥,𝑦 =2%, ∆𝜀 𝑧 =1%
Uniform input distribution
FODO – 2 pmq lengths – BPM and steerers – equipartitioned design – tune depression>0.4 – design done with uniform input distribution
Lund _12_02 Audit
Istituto Nazionale di Fisica Nucleare (Italy)

7. DTL design Tank 1 2 3 4 5 Cells 61 34 29 26 23 E0 [MV/m] 3.00 3.16
3.07
3.04
3.13
Emax/Ek
1.55
φs [deg]
-35,-25.5
-25.5
LTank [m]
7.62
7.09
7.58
7.85
7.69
RBore [mm] 10 11 12
LPMQ [mm] 50 80
Tun. Range [MHz]
±0.5
Q0/1.25
42512
44455
44344
43894
43415
Optimum β
2.01
2.03
1.91
1.84
Beam Det [kHz]
+2.3
+2.0
+1.8
Pcu [kW] (no margin)
870
862
872
901
952
Eout [MeV]
21.29
39.11
56.81
73.83
89.91
PTOT [kW]
2192
2191
2196
2189
2195

8. DTL Selected technologies
DTL normal conducting, PMQ focusing, internal BPM and steering dipoles for orbit correction, space for additional beam instrumentation in the tank transitions.
With this architecture the beam dynamics is very smooth, with short focusing period, to fulfill the emittance increase requirement.
The mechanical stiffness and geometrical accuracy is guaranteed by the thick stainless steel tank, and by the DT positioning system (CERN patent).
Key mechanical technologies
High precision machining
qualification of small parts, (DT) by CMM and
large pieces (tank) (laser tracker, arm..)
E-beam welding (Zanon, CERN….)
Vacuum brazing (in house)
Copper-plating of large tanks (two possible providers,
CERN and GSI)
CMM machine at INFN Padova
Istituto Nazionale di Fisica Nucleare (Italy)

9. Mechanical Design TANK (304L stainless steel)
internal Cu plating on finished surface internal Cu plating on finished surface (Ra 0,8) high stiffness support MASTER
GIRDER (EN AW5083 Al alloy)
Precise positioning of the DT stem axis in steel bushing SLAVE
Helicoflex
Vacuum tightness at stem/tank interface
Brazed joint
Rough sleeve
316LN
Sep. cylinder
304L
Rough DT body
CuC2-OFE
Beam pipe
Steerer (cables not represented)
Tank has function of master it is in ssteel internally cu-plated-girder has funciont of precise positioning of dt stem. Vacuum tighteness is provided at stem-tank and modules interface by helicoflex.
4 kind of DTs. DTs containing beam components are based on brazing tech with final ebw after insertion of beam component.
Steerer inserted from bottom side of DT and semicylinderebw.
Lund _12_02 Audit

10. DTL sub-systems and interfaces
Pumps
Valves
gauges
RF network
RF couplers
RF pick ups
Movable tuners and controllers (TCP/IP prot.)
Control system
Water cooling skid
Water cooling distribution
Local Control system (vacuum, cooling)
Steerer Power Supply
Support
Alignment refs
INFN
COOLING SYSTEM
Spoke section
MEBT
RF window
Heat exchanger
Valve
RF SYSTEM
Diagnostic
Intertanks
BPM signals
BCT inside DTL end flange
Valve
Vacuum SYSTEM

11. Interfaces 1 Cooling skid with 5 three-ways valves
Intertanks and tank covers
Pick-up and movable tuners
RF windows and supports
Vacumm manifold
Lund _12_02 Audit

12. Prototypes and high power test (planning and results)
Lund _12_02 Audit

13. PMQ Rare earth block specifications (Sm2Co17):
Error Br < 3%
Error an Angle < 2deg
Dimension tolerances < 0.05mm – 0.1mm
Br=1.1 T → Simulated Gradient=65 T/m
Assembly specifications:
Housing Material - Stainless Steel (316LN)
Outgassing rate per magnet below mbar l s-1
Gradient integral error (rms) %
Magnetic versus geometric axis: < 0.1 mm
Harmonic content at 10 mm radius: Bn/B2 for n=3,4,...10: < 0.01
Roll: 1 mrad
Goal:
define assembly criticalities
verify feasibility of specifications
define magnetic measurement bench and procedure
tunability of PMQ
Company qualification
Istituto Nazionale di Fisica Nucleare (Italy)

14. PMQ Rare earth block specifications (Sm2Co17):
Error Br < 3%
Error an Angle < 2deg
Dimension tolerances < 0.05mm – 0.1mm
Br=1.1 T → Simulated Gradient=65 T/m
Assembly specifications:
Housing Material - Stainless Steel (316LN)
Outgassing rate per magnet below mbar l s-1
Gradient integral error (rms) %
Magnetic versus geometric axis: < 0.1 mm
Harmonic content at 10 mm radius: Bn/B2 for n=3,4,...10: < 0.01
Roll: 1 mrad
Goal:
define assembly criticalities
verify feasibility of specifications
define magnetic measurement bench and procedure
tunability of PMQ
Company qualification
Istituto Nazionale di Fisica Nucleare (Italy)

15. Prototypes: PMQ Vacuum test
final pressure similar to the background value.
Larger amount of H2O, H2, O2, C02 These cannot be determined if they are from the AISI frame or from the PMs.
PMQ has been designed, machined (Stainless steel body) and assembled by INFN. Measured at cern it demonstrates to be compliant with specification.
Vacuum test performed at LNL shows not particular problems (final pressure, higher contents of, spike at 3.5 hours)
Istituto Nazionale di Fisica Nucleare (Italy)

16. Prototypes: PMQ
The PMQ prototype built and assembled at INFN-Torino has been measured with a rotating coil at CERN
The integrated gradient is 63.7 T/m and the harmonic content is lower than 1% at 7.5 mm radius
PMQ has been designed, machined (Stainless steel body) and assembled by INFN. Measured at cern it demonstrates to be compliant with specification.
Vacuum test performed at LNL shows not particular problems (final pressure, higher contents of, spike at 3.5 hours)
Istituto Nazionale di Fisica Nucleare (Italy)

17. Prototypes: BPM and EBW test
BPM: strip-line already brazed, waiting for coaxial feed-trough from USA
Mapper at LNL
BPM: brazed stripline at lnl. Waiting for coaxial feedtrough from usa company to be ebw on stripline. Mapper with micrometric motors and support for DT with BPM at LNL.
Possible weak point recognized on the EBW to be performed just on the brazing joint. First verification by simulation (hot spot rotating around the joint with CERn ebw parameters). Furtermore an order for testing in a dedicated Dt prototype have been placed at Zanon.
Istituto Nazionale di Fisica Nucleare (Italy)

18. Result of brazing and e beam welding test
EBW on Brazing possible weak point (T ebw > 1100°C, Tbrazing =850 °C)
Simulation shows non problem (Power_EBW=1800 W, v=12mm/s, spot volume=1mm3, brazed point < 650°C)
Tests have proven vacuum tightness and integrity (EDM slice)
ebw
brazing
Istituto Nazionale di Fisica Nucleare (Italy)

19. High Power test @ LNL Magic tee
2 solid state amplifiers 125 kW-CW each, 352 MHz.
Control system developed for multiple coupler feeding.
Waveguides and circulator at LNL.
IFMIF high power test stand now ready will be readapted.
High power DTL prototype from Linac4-CERN (peak power 180 kW, 10% duty cycle, E0=3.3MV/m) agreement KN2155/KT/BE/160L between CERN and INFN-LNL
3 drift tubes will be replaced by ESS drift tubes containing instrumentation + 1movable tuner for frequency control.
Ready for test in summer 2015 (delay of 6 moths due to amplifier delivery)
Magic tee
Final test will be an High power Rf test on the linac4 dtl prototype. We will use 2 solid state amplifiers. DT prototypes will be substitutes in the DTL.

20. Prototype schedule Deliverable no. Deliverables Delivery Deadline 1
Design, purchasing and installation of BPM test stand at INFN-LNL.
30/10/2014 2
Prototype production of a permanent magnet quadrupole (PMQ). Complete characterization of PMQ at CERN test bench.
30/11/2014 3
Prototype production of a BPM and Steerer to be installed in proper DTs.
30/03/2015
Construction and assembly of three complete DT prototypes with PMQ, with BPM and with steerer. Installation of DT prototypes in Linac4 DTL prototype.
30/05/2015 4
Design and construction of a movable tuner.
31/03/2015 5
Modification of the test stand used for IFMIF in order to test ESS components. 6
Tests of DT and tuner at nominal power and duty cycle (the DTL prototype developed by CERN and INFN-LNL will be used).
31/06/2015
3/6 months delay for prototyping.
Dts have been machined but we are going to use 2 of them fot the EBW test, they will be destroyed for inspection.
Istituto Nazionale di Fisica Nucleare (Italy)

21. Production sequence (TBC by CDR)
Forged cylinders production, tank machining, copper plating. Girder and other components, CMM and vacuum tests…
Production of the beam components (PMQ, BPM, dipole steerers)
Production of vacuum, support and inter-tank components
DT Brazed structure production (with cooling circuit tested)
Integration of the beam component in the DT
E-beam welding sealing, final tests on DTs
Assembly of the module (2 m), installation and alignment of the DTs
Assembly of the tank (4 modules), alignment, machining of the adaptation rings for relative position, tuning, tuners, ports, vacuum test,…
Installation and alignment of the tanks in the tunnel, installation of the intertank plates
Installation of vacuum, cooling, RF couplers….
NOTE 1-6 al INFN site, 7-8 DTL workshop at Lund, 9-10 in the tunnel
1-6 at LNL or in Italy
Then deliver to lund and done in the dedicated workshop
Finally after installation in the tunnel
Istituto Nazionale di Fisica Nucleare (Italy)

22. site requirements for DTLW
The DLTW is a "clean" and quite environment, temperature controlled (+1 deg over 30 min for bead pulling, +4 deg over the year).
About 13x 10 m is necessary for the assembly of the tank, separate space will be used for possible storing of assembled tanks.
The DTLW should be a closed part of a larger building, or in any case there should be a convenient entry space (for structures) before exiting outdoor (at least 10x8 m); such space can be shared with other labs; it is useful sometimes the possibility to enter this space with small vans or tracks. A small vestibule for people (about 2x2 m) is required.
A slow crane at least 3 tons inside the workshop for the assembly of the tank is needed.
The DTLW should be not far from the tunnel, a strategy to move the 8 tons tank into the tunnel will be defined by ESS.
Mechanical workshop for small interventions and adjustments should be accessible, electrical supply and compressed should be available.
Istituto Nazionale di Fisica Nucleare (Italy)

23. Preliminary Schedule 2014: conceptual design
Q1 2015: completion of critical prototyping phase
April 2015 Integration on site meeting
June 2015 CDR
2015: technical design phase, detailed drawings, tender for rough material
: construction (sequence: tank )
: assembly and tuning (sequence: tank ) :
installation and conditioning in the tunnel of tank
Installation conditioning and beam commissioning of tank 1 in the tunnel
Installation and conditioning of tank 2
beam commissioning of the 5 DTLs
Istituto Nazionale di Fisica Nucleare (Italy)

24. DTL organization at partner lab
Andrea Pisent (WU coordinator, LNL)
Francesco Grespan (deputy coordinator, LNL)
Paolo Mereu (Mechanics design, Torino)
Michele Comunian (Beam dynamics, LNL)
Carlo Roncolato (Vacuum system and brazing, LNL)
Marco Poggi (Beam instrumentation, LNL)
Mauro Giacchini (Local Control System, LNL, TBD)
LNL
Bologna
Torino
Istituto Nazionale di Fisica Nucleare (Italy)

25. Major Procurements Tank forged material (stainless steel)
OFE Copper parts
Stainless steel parts
RF windows
Movable tuners
Vacuum valves
Intertank boxes
Copper plating
Tank machining
Drift Tubes machining
E-beam welding
BPM production
Steerer dipoles (design, production)
PMQ (material, machining, field test)
Supports
Cooling skid and cooling circuit components
Istituto Nazionale di Fisica Nucleare (Italy)

26. Top risks
Beam performances in beam commissioning (61 tubes in tank 1 and final).
DT alignment.
DT production (QA, mainly dimensions, vacuum and water tightness).
Copper plating quality
Intertank integration
Logistics: assembly of the tank in the DTW, transport to the tunnel…..
RF conditioning
Istituto Nazionale di Fisica Nucleare (Italy)

27. Next Six Months
CDR
Completion of mechanical specs and production drawings
Completion of critical prototypes
Forged tank procurement for the 1st module
Launch the RF window procurement
Istituto Nazionale di Fisica Nucleare (Italy)

28. Summary
The DTL is a large and complex part of the ESS linac. Respect to the successful Linac4 CERN we shall have higher energy and duty cycle.
The overall linac performances are crucially determined by the quality of the DTL realization.
The DTL design has been optimized for best beam performances, the main technological choices are been tested with prototypes.
In June we shall have the CDR, necessary to launch the first procurements.
Istituto Nazionale di Fisica Nucleare (Italy)