The RFQ for IFMIF-EVEDA project: status and high-power tests.

The RFQ for IFMIF-EVEDA project: status and high-power tests. Enrico Fagotti INFN-LNL Michele Comunian INFN-LNL

International Road Map Advanced Materials are at a critical path ITER DEMO < 150 dpa 1-3 dpa/lifetime IFMIF Dpa: displacement per atom: measure the integral of received radiation 20-40 dpa/year International Fusion Materials Irradiation Facility

IFMIF Principles Test Modules 2 x 125 ma D + CW at 40 MeV Accelerator based neutron source using the D-Li stripping reaction intense neutron flux with the appropriate energy spectrum Typical reactions: 7 Li(d,2n) 7 Be, 6 Li(d,n) 7 Be, 6 Li(n,T) 4 He Beam footprint on Li target 20cm wide x 5cm high (1 GW/m 2 )

A specific source is needed to simulate DEMO The accumulation of gas in the materials lattice is intimately related with the neutron energy 54 Fe(n,α) 51 Cr (incident n threshold at 2.9 MeV) and 54 Fe(n, p) 54 Mn (incident n threshold at 0.9 MeV) Swelling and embrittlement of materials takes place Neutron flux compared with DEMO s in available and planned neutron sources Spectrum fission n Steven J. Zinkle, A. Moeslang, Evaluation of irradiation facility options for fusion materials research and development, Nuclear Engineering & Design, pre-printed (2013)

Example of after irradiation test of small speciments

Facility design

Accelerator facility of IFMIF 2 x 5 MW beams the highest intensity the highest beam power the highest space charge 10 the longest RFQ Individual availability of >90% D + source CW 140 ma 100 kev RFQ 175 MHz 5 MeV SRF Linac HWR 175 MHz 40 MeV 2 accelerators, 2 x 125 ma, 2 x 5MW Juan Knaster IPAC A Pisent 2013 SIF - Shanghai 2013 Beam shape 2 7

Linear IFMIF Prototype Accelerator A Pisent Follow up Jannuary 2012

Linear IFMIF Prototype Accelerator A Pisent Follow up Jannuary 2012

RFQs general parameters Name Lab ion energy vane beam RF Cu Freq. length Emax Power density voltage current power power ave max MeV/u kv ma kw kw MHz m lambda kilpat W/cm 2 W/cm 2 IFMIF EVEDA LNL d 2.5 79-132 130 650 585 175 9.8 5.7 1.8 3.5 60 pulsed CERN linac 2 CERN p 0.75 178 200 150 440 202 1.8 1.2 2.5 SNS LBNL H- 2.5 83 70 175 664 402.5 3.7 5.0 1.85 1.1 10 CERN linac 3 LNL A/q=8.3 0.25 70 0.08 0.04 300 101 2.5 0.8 1.9 CW LEDA LANL p 6.7 67-117 100 670 1450 350 8 9.3 1.8 11.4 65 FMIT LANL d 2 185 100 193 407 80 4 1.0 1 0.4 high p IPHI CEA p 3 87-123 100 300 750 352 6 7.0 1.7 15 120 TRASCO LNL p 5 68 30 150 847 352 7.3 8.6 1.8 6.6 90 CW SARAF NTG d 1.5 65 4 12 250 176 3.8 2.2 1.6 mid p SPIRAL2 CEA A/q=3 0.75 100-113 5 7.5 170 88 5 1.5 1.65 0.6 19 CW ISAC TRIUMF A/q=30 0.15 74 0 0 150 35 8 0.9 1.15 - - lp PIAVE LNL A/q=6 0.58 280 0 0 8e-3 (SC) 80 2.1 0.5 - - - The RFQ is INFN Italy responsibility LNL Padova Torino..Bologna Cryo pump Tuner RF coupler 0.55 m module IFMIF-EVEDA RFQ 18 modules 9.8 m Powered by eight 220 kw rf chains and 8 couplers High availability 30 years operation. Hands on maintenance First complete installation in Japan

RFQ system organization Responsible A. Pisent Responsible for Padova: A. Pepato Responsible for Torino: P. Mereu Responsible for Bologna: A. Margotti Padova Legnaro Bologna About 30 persons involved, 20 FTE, 10 dedicated contracts Torino The participation of INFN to IFMIF-EVEDA includes RFQ construction Participation to final IFMIF design activity Participation to the man power of the project team in Japan Participation to beam commissioning in Japan INFN organization 11

IFMIF/EVEDA Accelerator building by JAEA (Rokkasho)

IFMIF RFQ modulation design Ions d Energy range 0.1-5 MeV input-output nom emitt 0.25 mmmrad (rms) Ouput long emitt. 0.2 MeV deg (rms) Output current 0.2 Tansmission 98 % WB distr. 95 % Gsussian distr. The voltage is increased (79-132 kv) following an analytic law The focusing in the Gentle Buncher is strong (B=7) so to keep the tune depression above 0.4 for the best control of space charge. Main resonances are avoided in the accelerator section The focusing in the shaper raises from 4 to 7 to allow an input with smaller divergence.

neutrons [n/(s*m)] Power Loss [W/m] Current Loss [ua/m] 6 5 4 3 2 1 0 250 200 150 100 50 Current Loss [ua/m] 0 200 400 600 800 1000 RFQ Power Length Loss [cm] [W/m] Integral 0.96 ma Integral 363 W Serie1 Serie1 Beam losses To achieve Beam losses concentrated in the low energy part is very important since neutron production is proportional to w 2 0 0 200 400 600 800 1000 1.60E+09 1.40E+09 1.20E+09 1.00E+09 8.00E+08 6.00E+08 4.00E+08 2.00E+08 0.00E+00 Neutron RFQ production Length [cm] [n/(s*m)] Integral 2.4 10^9 n/s 0 200 400 600 800 1000 RFQ Length [cm] Serie1 n 7 2.1 5.15*10 Nw WB distribution 0.25 mm mrad rms norm

IFMIF EVEDA RFQ challenges 650 kw beam should be accelerated with low beam losses and activation of the structure so as to allow hands-on maintenance of the structure itself ( Beam losses<10 ma and <0.1 ma between 4 MeV and 5 MeV). (Tolerances of the order of 10-50 um) 600 kw RF dissipated on copper surface: necessity to keep geometrical tolerances, to manage hot spots and counteract potential instability. The RFQ will be the largest ever built, so not only the accelerator must be reliable, but also the production, checking and assembling procedure must be reliable Fully exploit INFN internal production capability (design machining, measurement and brazing) Make production accessible for different industrial partners At present and we are in the production of the modules phase. 9/18 have been accepted today

Modules construction

RF cavities built in three supermodules (6 modules each) High energy SM in construction at Cinel, Padua (Italy), Intemediate energy in INFN Padova, Low energy by RI Koln (Germany)

Main news Module production: Cinel production completed (6 modules), INFN production, 6/6 final machining, 2/6 brazed (one need repairing). RI electrodes machined, brazing late High power tests Segment (four modules) tuned to 175 MHz and +1% The high power test stand (approx 500 kw installation) is fully operational. The couplers by JAEA have shown unacceptable power losses at the window. As a risk reduction procedure a new couple couplers have been designed and built by INFN (machining and detailed mechanical design at CINEL) INFN couplers have been tested to the nominal power of 200 kw cw RFQ inside view RFQ couplers by INFN

Mechanical design Based on vacuum brazing, LNL mechanical experience with TRASCO, CERN experience for RFQ brazing, design compatible with oven at CERN, LNL and in industry; Due to the relatively large transverse dimensions of the RFQ, the procurement of the CUC2 raw material blocks is limited by the total mass amount (length 550 mm). To minimize the use of Ultra-pure CUC2 and to limit the induced stresses on the raw material, a rough-cut of the shape of the module components from a starting block of about 500x280x570 mm will be performed, by using a EDM (wire electroerosion). The accelerator is composed by 18 of these modules. Prototype before brazing at CERN Brazing joint T Brazing joint E

Mechanics details Head flange 65 0 Vacuum grids machined from bulk

water-in Cooling circuit About 600 kw RF power are removed by means of 28 channels longitudinally drilled along the RFQ modules; the water velocity is approximately 3 m/s, 12 channels at fixed low temperature on the vanes 16 channels on the cavity wall with variable temperature for frequency tuning the temperature of the channels on the vane and on the cavity wall can be separately tuned so to achieve a tuning range of +100kHz. 3 modules are in series (supermodule water-out water-out water-in module (~0.55 m) super-module (~3.3 m) 9.78 m

3D details Slug tuners (CF100) Dummy tuners, vacuum grids and end cells In the end cell the 45 angle of the undercut guarantees the access of the cooling channel as close as possible to the hot spot at the electrode base (~80 W/cm2*), which is the most severe of the entire RFQ Deformations of 70 um and field perturbation less than 1% Tuning range +1 MHz 70 deg C *with margin of 10% higher field

First construction step module n. 16 Rough machining of block 550 mm long via EDM for minimal stresses and deformations during annealing and brazing EDM at Padova Remaining copper 550 mm electrode before cleaning

Finishing 0.7 µm roughness 3D modulation 20 µm tolerances on vane tip geometry

Point 39 Characteristic: Curve Form Full Profile Z 1 mm Segment: Segment 001 Lower Tolerance: -0.0200 mm Upper Tolerance: 0.0200 mm Deviation: 0.1073 mm Position: X: -201.1000 mm Direction: X: 0.0000 mm Y: -1.0000 mm Z: 0.0000 mm Status: Valid Point 1336 Characteristic: Curve Form Full Profile Z 1 mm Segment: Segment 001 Lower Tolerance: -0.02 00 mm Upper Tolerance: 0.0200 mm Deviation: 0.0342 mm Position: X: 7.7707 mm Y: -176.8850 mm Z: 1.0000 mm Direction: X: 0.9397 mm Y: -0.3420 mm Z: 0.0000 mm Status: Valid Point 1461 Characteristic: Curve Form Full Profile Z 1 mm Segment: Segment 001 Lower Tolerance: -0.0200 mm Upper Tolerance: 0.0200 mm Deviation: 0.0186 mm Position: X: 17.9900 mm Y: -133.6060 mm Z: 1.0000 mm Direction: Z: 0.0000 mm Status: Valid Point 2353 Characteristic: Curve Form Full Profile Z 1 mm Segment: Segment 001 Lower Tolerance: -0.0200 mm Upper Tolerance: 0.0200 mm Deviation: 0.1070 mm Position: X: 192.5520 mm Y: -67.5000 mm Z: 1.0000 mm Direction: X: 0.0000 mm Y: -1.0000 mm Z: 0.0000 mm Status: Valid Part Number 8 Meas. Plan Name Calypso 4.10.06 Date September 29, 2 Carl Zeiss Order Four electrodes of module #16 electrodes CMM Type Drawing No. Department: ACCURA_MASS Operator IFMIF 0016049000 Signature: (machined by Cinel) in specs 1: Curve Form Full Profile Z 1 mm X -200.0000-150.0000-100.0000-50.0000 0.0000 50.0000 100.0000 150.0000 200.0000-50.0000 Y: -67.5000 mm Z: 1.0000 mm art Number eas. Plan Name Calypso Max 4.10.06 Y Deviation: X 18.6 mm No Identifier Sigma [mm] Form [mm] CMM Type ACCURA_MASS 0016043000 Number of Points Lower Tol. [mm] Upper Tol. [mm] X: 1.0000 mm Y: 0.0000 mm material stock Carl Zeiss Drawing No. -100.0000-150.0000-200.0000 Min Dev. Max Dev. MinInd MaxInd Best Fit X [mm] Y [mm] Z [mm] X Y Z [mm] [mm] Y 0.2 mm 50 : 1 Date September 15, 2 Order Department: Operator Signature: IFMIF 1 Curve Form Full Profile Z 1 mm 0.0362 0.1255 2396-0.0200 0.0200-0.0169 13 0.1086 730 Translation Rotation 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Max Deviation: 10.5 mm Max Deviation: 6.1 mm Z -250.0000-200.0000-150.0000-100.0000-50.0000 0.0000 50.0000 100.0000 150.0000 200.0000 250.0000 Y Y

INFN development for Brazing Necessary for the large production (18 modules could not be done at CERN). Vacuum oven in INFN LNL

Brazing at LNL (1/2) Upgrade of the vacuum system Construction of the assembly lab Test of brazing geometry with test pieces. Ultrasonic check of brazing

Brazing at LNL (2/2) Chemical preparation Brazing

Succesfull Brazing at LNL and Cinel of two small prototypes (half scale transversally) Construction of the assembly lab One step vertical Ultrasonic check of brazing Chemical preparation Brazing Vacuum ok dimensions not significative

Module 16 brazing After first brazing (Vertical, Cinel) vacuum and dimensions were ok After second brazing (Vertical) Vacuum leak reparing on vacuum port and severe problems with brazing of head flange Istituto plates. Nazionale di Fisica Deformation Nucleare (Italy) at the limit of PA acceptance (100 um, 1 MHz)

INFN production of modules Machining and QA at INFN Padova Chemical processing at LNL Assembly at LNL (sez pd responsibility) Brazing by LNL

High power test stand at LNL A 500 kw test stand able to test 4 RFQ modules, to test at full power density the structure (200 kw RF power) The test is necessary to validate the design during the module construction (it was ment to be used at the beginning, now we have built half of the modules)

JAEA couplers history All the components for coupler test-stand arrived to LNL at the beginning of July 2013. Before connecting the system to the RF line, a Network Analyzer was used to measure RF properties. Couplers resulted to be underperforming: 25% power losses

Backup Solution A new RF Power Coupler was designed Nov 2013 A new coupling cavity was designed Nov 2013 Two new RF windows were ordered Nov 2013 and delivered to LNL Feb 2014 The two couplers were machined (CINEL) Feb 2014 and brazed (LNL) Apr 2014 The new coupling cavity was produced (CINEL) Apr 2014 A new coupler test-stand was assembled May 2014 Coupler conditioning started 25-May-2014 Status Input power (kw) Duty Cycle (%) 27/05/2014 200 0.02 28/05/2014 200 2.50 29/05/2014 150 100 03/06/2014 200 100

Power Coupler - Concept Coupler and RF window are two separate devices coupled with a standard 6-1/8 IEC coaxial interface Coupler material is copper OFHC Water heat exchange coefficient is maintained near 10000 W/m 2 K in the whole heat exchange surface: water velocity is above 2.5 m/s both in the external and internal spiral and in the loop Coupler inner connection is used to remove power from the RF window

HPC Machining and brazing

High Power Couplers

HPC test-stand assembly and measurements S 12 = -0.34 db (7.6% insertion loss) (with dummy couplers) S 12 = -0.44 db (9.7% insertion loss) (with final couplers without joints)

HPC test-stand control system

RFQ alignment (outside view)

RFQ alignment (inside view)

RFQ Tuning for the High Power Test 1. Tuner flush and end plates @ nominal settings (g=12 mm insertion each): Mode Spectra Q modes fq0=174.77 MHz fq1=190.79 MHz fq2=226.52 MHz Q0 (fq0) = 7040 D modes fd0=171.38 MHz (degeneracy= 10 khz) fd2=190.86 MHz (degeneracy= 30 khz) fq2=228.68 MHz (degeneracy= 50 khz) Beadpull measurements (metallic bead) Dipole components are very low: Strong Q component tilt at LE side Due to the P2 module frequency mismatch 03/06/2014 44

RFQ Tuning for the High Power Test (2) 3. Measurement after 2 tuning steps fq0=175.014 MHz The attainment of the maximum value of ± 2% voltage perturbation is verified almost everywhere in the RFQ. The zone exceeding this value is related only to the P2 RF plug. 4. Measurement after the insertion of the dummy coupler fq0=175.001mhz The dummy coupler had only a very slight effect on both fq0 and voltages.