sc elliptical cavities design and associated r&d max mid-term design review

SC Elliptical cavities design and associated R&D

MAX mid-term design review

12/13 NOVEMBER 2012, SCK•CEN, BrusselsR. Paparella, INFN Milano

On behalf of the task 3.1 team

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Layout of the talk

Elliptical cavitieso RF design from ASH/TRASCO collaborationo Cavity manufacturing and cold testo Helium tank integration, magnetic shielding and fast tuner

ADS cryomodule test stando Cryostat thermal design o Manufacturing and assembly at SIMIC

Experimental resultso Commissioning at IPNOo Review of performed cold tests

Current status and perspectives

R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

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The b = 0.47 cavity – RF design

Cavity final design at 704.4 MHz has been the result of the TRASCO/ASH collaboration, exploiting a fully parameterized model of a SC cavity


Full parametric model of the cavity in terms of few meaningful geometrical parameters:o Ellipse ratio at the equator (R=B/A)

Ruled by Mechanicso Ellipse ratio at the iris (r=b/a)

Epeako Side wall inclination (a)

and position (d) Epeak vs. Bpeak tradeoff and coupling k

o Cavity iris radius Riris Coupling k

o Cavity Length L b

o Cavity radius D used for frequency tuning

Behavior of all e.m. and mechanical properties has been found as a function of the above parameters

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The b = 0.47 cavity – figures


Frequency 704.4 MHzCavity b 0.47Number of different cell geometries 3Cell type Int. Ext left Ext right

Half-cell length [mm] 50 50 50Iris radius [mm] 40 40 65Equator ellipse ratio, R 1.6 1.7 1Iris ellipse ratio, r 1.3 1.3 1.3Wall angle [deg] 5.5 5.98 4.84Wall distance [mm] 7 7 6Cell-to-cell coupling [%] 1.34Phys. cavity length [mm] 830Number of cells 5Epeak/Eacc 3.57Bpeak/Eacc [mT/(MV/m)] 5.88r/Q [Ohm] 90Stiffening radius [mm] 70KL [Hz/(MV/m)2] (inner cell, inf stiff) -3.5

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The b = 0.47 cavity – prototypes

Two low and two high RRR single-cell prototypes built within TRASCO:o Built by E. Zanon (Italy)o Treated at CEA-Saclay and JLAB with BCP, HPWR and class 100 CR assemblyo Vertically tested at CEA-Saclay, JLAB and LASA


1E+08

1E+09

1E+10

1E+11

0 5 10 15 20 25 30

Qo

Eacc (MV/m)

Z1 03 A1 T=2K

électrons

1,00E+09

1,00E+10

1,00E+11

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

Q0

Eacc [MV/m]

Single cell cavity TRASCO b=0.47Q0 vs. Eacc

Test #3

Design goal

6R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

The b = 0.47 cavity – building the cavity

Dimensional and RF test on half-cells and on dumb-bells for QC Soft-BCP to clean the welding region Reduced number of welds, time-dominating factor is the pump down

and the cooling after welding

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The b = 0.47 cavity – 5 cell cavity

Defined the production choosing all the technological solutions NbTi Flanges based on TTF/SNS solution Ready for Titanium Helium Vessel (with stiffening TIG welded) Dummy HOM ports


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The b = 0.47 cavity – 5 cell cavity vert tests

Ep/Eacc=3.57 , Bp/Eacc=5.88 mT/(MV/m) Z501 – JLAB 31/03/2004 , Z502 – Saclay 24/06/2004


0 2 4 6 8 10 12 14 16 18 20

109

1010

start of electron emission

Test #1 limited by strong field emission

Q0

Eacc [MV/m]

Z501 Z502 - before conditioning Z502 - after conditioning Design Value

multipacting barriers

Q0

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The b = 0.47 cavity – toward dressed cavity

A special setup has been built on purpose for cavity FF and goal frequency tuning

Helium tank realized to fulfill external stiffness requirements


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The b = 0.47 cavity – magnetic shield

Both inner cryoperm shield in tank and outer m-metal shield in warm region solutions have been investigated

Finally, internal designed has been fixed Pre-assembled to measure the shielding and compare to simulations


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The b = 0.47 cavity – coaxial blade tuner A coxial blade tuning system has been designed, inspired by the model realized by INFN for TESLA

cavities. A moving steel leverage transfers, through deforming Ti blades, the tuning action of stepper motor

drive unit.o Design tuning range of 300 kHz with 1 Hz/step sensitivity

Two piezo actuators allow for fast and fine tuningo Design static tuning range of about 10 kHz with both actuators energized with 200 V


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The ADS cryomodule test stand


Short, single-cavity module jointly realized by INFN Milano and IPN Orsay as EUROTRANS project deliverable: INFN

Cavity+Module IPNO

Coupler, Valve box & test infrastructure

Module based on theconcept of short independently fed and rapidly exchangeable units

Will be used for long testing for the reliability characterization of components

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The cryomodule – cavity frame


Cavity power coupler orientation is vertical Reference for supports is CEBAF solution Cavity space frame simplifies assembly and

handling of the cavity after CRo No need for vertical movements

Kept minimal longitudinal space (flat heads vs standard PV dome heads)

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The cryomodule – cryogenics


Helium buffer in the module Liquid helium line for coupler cooling Valve box from IPN

Circuit 4.3K Circuit 1.9K

Shield

(W)Static(W)

Dynamic

(W) (W)Transfer Line 0.5 Cold box 2.0 20.0Cryomodule 4.0 25.0 50.0Coupler 1.2 0.0

Total 3.7 4.0 25.0 70.0 32.7

Mass flow (g/s) 1.70 0.45

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The cryomodule – manufacturing


Cryomodule has been manufactured by SIMIC firm at Camerana (Italy) Delivery to IPNO in March 2010

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The cryomodule – IPNO Experimental area


RF source 160 kW DC PS 80 kW IOT Waveguide, doorknob transitions Power coupler, test bench Cryogenics valve box and controls

End 2007

Beginning 2011

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Power coupler


Based on the SNS design (itself derived from the Tristan

coupler)

Conditioning cavity

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Results – RF power supply & conditioning


Coupler conditioning:o Test bench equipped with tunable cavity with copper plunger,

baking, vacuum management and diagnosticso Couplers and cavity baked at 130°C → vacuum up to 5.10-8 mbar,

no leak detected on the ceramic windowo A first travelling wave (CW) conditioning at 1kW has been

successfully done (E. Rampnoux & S. Berthelot, IPNO) RF circulator

o Circulator efficiency is very sensitive to temperature & the regulation system of the coil is slow

o Several Breakdowns / Flash occurred in the DC power supply (40 kV – 4 A). Two modules sent to Bruker for assessment.

o DC power supply has been repaired and electric insulation improved. It can now be controlled through a Labview program (C. Joly, IPNO)

IOTo The IOT has been successfully re-re-re-tested with its RF

circulator in full reflection until 80 kW. The current of the circulator coil had been tuned to enable fast RF power increase (switch on/off). (J. Lesrel, IPNO)

o In Sept. 2012 the coupler test stand was assembled to the IOT: now almost ready for high power conditioning.

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Results – critical coupling cold tests


Critical coupling – no power coupler:o Understand the complete cryogenic system behavioro Q0 measurement @ 4K & 2Ko Check the good behavior of the RF Phase Locked Loop (PLL)o Measurement of the static capabilities of the tuning system : stepper motoro Fast tuning systems influence : range of detuning & piezos Transfer Function

Overview of the tests campaigno 1st test : - July 2010 - Big leakage on the He tank detected. Experiment stopped & cavity

travelled back to ZANON.o 2nd test : - February/March 2011 - New leakage on the He tank – test at 4 K but we encountered

problems with the PLL : not able to power correctly the cavity.o 3rd test : - October 2011 – cavity characterization at 1.9 K.o 4th test: - May 2012 – cryogenic characterization of cryomodule and cryo-plant.

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Results – 1st cold test


Cavity send back to Zanon for repairingo The weld was partially removed and soldered with argon gas-filled

Then at LASA for leak check and field flatness measurementso Thermal cycles with nitrogen and no leak detected after warm-up

Repairing of the cold leak, Oct-Nov 2010

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Results – 1st cold test


Field flatness has moved : bead-pull measurement

Coupler side

Pick-up side

Guilty one cell on the coupler

side detuned

Matrix analysis give individual freq cell frequency &

field shapes of the five

modes

Cavity Performances expected to decreased by ~20 %.

Unflatness

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Results – 2nd cold test


Experimental results Measurement of the cryogenic procedure only at 4K (2K pumping system was not ready). Cryogenics control systems had been finalized (A. El Tarr, IPNO)

o Siemens PLC to collect data, control valves and manage cryogenics and vacuum safety as vacuum loss or quenches

o Labview interface to handle the whole cool-down procedure and acquire data

Stepper motor tuning range measured: ~ 270 kHz @ 4 K

Issues and adjustments after the test Improvements of cool-down piping A new leakage appeared on He tank

o Repaired at IPNO and N2 thermal shock applied

New PLL filter loop hardware Module RF feedthrough replaced

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Results – 3rd cold test

No leak anymore on the tank → repairing procedure confirmed

March 2011

October 2011

Static losses : ~ 7.5 W (@ 2 K) (N. Chevalier) & ~ 5.5 W (@ 4 K - module closed on it self) Further improvements:

o « warm » point detected at the Cryomodule/valve box connectiono Level probes in the helium pot need to be gaugedo A direct reference for the pressure on the helium bath must

be provided for accurate automated regulationo Some thermal sensors were poorly “thermalized”


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Measurement at ~ 1.9 K (Rsurf ≈ 9 nΩ; RBCS ≈ 3 nΩ → Rres ~ 6 nΩ)

27/10/2011 afternoon (T ~ 1,9K)

Le 27/10/2011 morning (T ~ 2.0 K)

the 12/10/2011 (T ~ 4.2 K)

multipacting

Processing

RF cable limits (breakdown @ Pinc ~ 170W)

Quench

Coupling : _ Qi ≈ 2.0 1010

_ Qt ≈ 2.3 1011

(@ βg=0.47)R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

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Motor ■ Measured hysteresis on small displacement (~ 0.1 mm) of 2kHz■ After a few cycle motor action was blocked : Screw and nuts seized!!

Piezo actuators ■ Effect below expectation by one order of magnitude:

+150V → ~200 Hz detuning. ■ Measurement only achieved at 4K, with a high sensibility to pressure

variation.■ Cabling and installation sequence to be cross-checked

SEIZED !?

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Results – understanding motor seizing


No large failing has been detected, just clear evidences of high level of friction. The rather large quantity of copper stripped in one point could be the major responsible for the actual seizing.

Analysis of the story of motor unit revealed that CuBe shaft has not been heat-treated / hardened: big impact on material strength as well as surface hardness.

These drive units produced by INFN and used so far are going to be replaced by XFEL-compliant drive units that have been already purchased (delivery expected within October) within MAX funding.o These units will be the exact replica of XFEL ones, taking therefore full benefit of DESY expertise

and quest for reliability.

1.5 mm

Copper deposition on one steel nut thread surface

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Reliability is taken into account when choosing actuators:o Both stepper motor and piezoelectric ceramic are robust and proven technologies, almost a

standard solution in the field of SC cavities fast tuning.o Failures occurred in prototypes along their

“learning curve” phaseo The large data set available from manufacturers has been

integrated in the last 15 years with continuous use and several dedicated cold tests in different labs

Warm vs. Cold motor is sometimes discussedo That is also accessibility vs. static heat loads

(see S1G at KEK) Piezoelectric actuators:

o No moving parts, no lubricant, predictively functional at cryogenic temperature

o Radiation hardness verified (M. Fouaidy, IPNO, 2004)– 100 times the expected dose in operation

o Life-time tests conducted (A. Bosotti, R. Paparella, INFN, 2005 and 2012)– >10^9 (10 y equivalent work load) at cold in both

unipolar and bipolar mode

Jean-Luc Biarrotte, MAX 4th general meeting, Frankfurt, October 1-2, 2012.

Results – Cold actuators reliability

M. Fouaidy et Al., CARE Report, 2004

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Results – 4th cold test


The module and the cryogenic installation are fully qualified & we set-up a system which enable to have an accurate control of the helium bath temperature

o Measured performances in agreement with expectations : at 1.9 K one can operate the module until ~35 W heat load on the cavity + ~ 6 W static losses

Further improvements:o Warm point at interconnection valves box / cryostat is confirmed and have small losses:

not a big issue.o New probes with controls will be ordered to AMI in replacement of home-made oneso Investigation on thermal sensor shift in progress (maybe heat load from cables)

Control example at 1.9 k (P = 23 mbar)2 K tests balance

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Perspectives


Except few instrumentation details the module is now fully operational on the cryogenic point of view

o We are currently moving the helium pumps (primary + roots) to its final configuration in a new building. Ready for January 2013.

The power coupler conditioning will start very soon and we plan a 2 months period for the test : October - November 2012

A clean room session has to be foreseen for December 2012: for the power coupler assembly.

The Module preparation and wave guide installation is planned for: December 2012 / January 2013.

First High Power test : February / March 2013.

sc elliptical cavities design and associated r&d max mid-term design review

Documents

cavity ff

cavity dimensional

cavity figuresr

cell cavity vert testsepeacc

cavity magnetic shiel

cell coupling

cavity prototypestwo

welding nthe b