the new freia laboratory for accelerator...

THE NEW FREIA LABORATORY FOR ACCELERATOR DEVELOPMENT

R. Ruber, A.K. Bhattacharyya, D. Dancila, T. Ekelöf, K. Fransson, K. Gajewski,V.A. Goryashko, L. Hermansson, M. Jacewicz, T. Lofnes, M. Olvegaard, A. Rydberg,

R. Santiago Kern, R. Wedberg, R. Yogi ∗, V. ZiemannUppsala University, Sweden

Abstract

The FREIA laboratory is a Facility for REsearch Instru-mentation and Accelerator Development at Uppsala Uni-versity, Sweden, constructed recently to develop and testaccelerator components. Initially it will develop the RF sys-tem for the spoke cavities of the ESS linac and test prototypespoke cavities at nominal RF power. For this purpose weinstalled a helium liquefaction plant and will soon recieve aversatile horizontal test cryostat and two 352 MHz RF powerstations, one based on two tetrodes and the other on solidstate technology. Beyond these developments FREIA willhouse a neutron generator and plans for a THz FEL are underdiscussion. FREIA is embedded in the Ångström physics,chemistry and engineering campus at Uppsala in close prox-imity to mechanical workshops, clean room with electronmicroscopes, tandem accelerator and the biomedical center.

INTRODUCTION

Uppsala University has a long standing history of physicsresearch with well known names as Anders Celsius andAnders Ångström in the 18th and 19th century and sev-eral Nobel Laureates in Physics during the 20th century.Theodore Svedberg, Nobel Laureate in 1926, initiated ac-celerator based research in Uppsala during the 1940s andconstruction of a 185 MeV cyclotron was completed in theearly 1950s. During the 1980s the cyclotron was upgradedand a 1.36 GeV proton accelerator and storage ring, CEL-SIUS was constructed. The CELSIUS ring was closed downin 2006 while the cyclotron was kept open but is now mainlyused for proton therapy and as irradiation facility for elec-tronics testing.

Since 2006, the accelerator physics group at UppsalaUniversity has been participating in the development ofthe CTF3/CLIC electron-positron collider, the FLASH andXFEL free-electron lasers and the European SpallationSource (ESS), concentrating on microwave (RF) power andinstrumentation projects. With the 2009 decision to con-struct the ESS in Sweden, it was proposed to build a teststand for high power RF and superconducting cavities inUppsala: The new FREIA Laboratory for accelerator andinstrumentation development.

The new FREIA Laboratory has been designed and builtaround it first task to provide a test facility for supercon-ducting spoke cavities and their high power RF systems. Inaddition it provides cryogenic fluids such as liquid heliumand nitrogen to experimental groups at the university. The

∗ presently at ESS

layout of FREIA is shown in Figure 1. The main equip-ment consists of HNOSS, a horizontal test cryostat, a heliumliquefier, high power RF transmitters and several concretebunkers. The infrastructure of FREIA has been designed toaccomodate modest future extensions for other test facilitiesand experiments.

MAIN EQUIPMENT

The main resources of the FREIA Laboratory are its com-petent staff and a new set of state-of-the art equipment re-quired for a superconducting accelerating cavity test stand:helium cryogenic system, test cryostat and RF power station.

Cryogenics

A Linde L140 liquefier has been installed delivering over140 l/h of liquid helium into a 2000 l storage dewar. Thestorage dewar has 4 connections: one to fill mobile dewarsand three with integrated cold valves to connect transfer linesto experiments. The helium gas recovery system includes a100 m3 gas balloon and three 27 m3/h recovery compressors.A 20,000 l liquid nitrogen storage dewar, outside the building,provides the liquid nitrogen for the liquefier pre-cooling andalso for the filling of mobile dewars. These installationswere commissioned in March and since then the FREIALaboratory has taken up the task to provide the cryogenicsneed for experiments all over the university. Details aredescribed elsewhere [1].

Test Cryostats

FREIA has designed a versatile horizontal cryostat calledHNOSS (Horizontal Nugget for operation of Superconduct-

cryogenics

RF equipment

3 bunkers withtest stands and

horizontal cryostat

vertical cryostat

control room

bridge toÅngströmLaboratory

Figure 1: Layout of the FREIA Laboratory.

5th International Particle Accelerator Conference IPAC2014, Dresden, Germany JACoW PublishingISBN: 978-3-95450-132-8 doi:10.18429/JACoW-IPAC2014-THPRO077

07 Accelerator Technology Main SystemsT21 Infrastructures

THPRO0773059

Cont

entf

rom

this

wor

km

aybe

used

unde

rthe

term

soft

heCC

BY3.

0lic

ence

(©20

14).

Any

distr

ibut

ion

ofth

isw

ork

mus

tmai

ntai

nat

tribu

tion

toth

eau

thor

(s),

title

ofth

ew

ork,

publ

isher

,and

DO

I.

ing Systems1) for test of superconducting accelerator cavi-ties, magnets or other devices [1, 2]. The idea of HNOSS isbased on HoBiCat and likewise it can accept two supercon-ducting accelerating cavities simultaneously. Its dimensions,3.2 m internal length by 1.3 m diameter, and access portsare designed to accomodate both TESLA type 1.3 GHz andESS type 704 MHz elliptical cavities as well as ESS type352 MHz double spoke resonators. HNOSS has an inte-grated internal magnetic shield and a valve box located ontop as shown in Figure 2. The temperature operation range isdown to 1.8 K with up to 100 W heat load. HNOSS is underconstruction in industry with delivery foreseen in August.

FREIA is planning to design and acquire a vertical cryostatin the near future.

To operate the test cryostats below the 4 K range of heliumprovided by the liquefier, a sub-atmospheric pumping stationwill be connected. To this end an integrated station witha set of roots and dry-pumps has been ordered with a flowcapacity of 10 g/s at 200 mbar down to 3.2 g/s at 10 mbar(room temperature).

RF Equipment

As has been reported earlier [3], the technology and lay-out of the RF power stations have been chosen based onthe requirements to test ESS type 352 MHz double spokeresonators: 400 kW peak power with 3.5 ms pulse lengthand 14 Hz repetition rate. Two stations are needed to powertwo spoke resonators inside a single cryostat simultaneouslyand individually. The first transmitter is ordered from indus-try [4]. Final integration has unfortunately been delayed dueto external factors but delivery is still foreseen this year. Thesecond transmitter will be ordered after commissioning ofthe first.

Both coaxial 6 18 inch and WR2300 half height waveguide

lines will be used for the RF distribution. The coaxial linehas enough margin for 400 kW peak power and is smaller

1 In Norse mythology, Hnoss is one of Freia’s daughters.

Figure 2: The HNOSS horizontal test cryostat.

Figure 3: Layout of the RF power station.

than a waveguide line, but both are installed in order to testequipment for the ESS RF distribution.

Bunkers

Three concrete bunkers have been constructed for experi-ments producing ionizing radiation. The largest bunker hasinner dimensions of 10.4 m length by 4 m width and 4.8 mheight. It will be equipped with HNOSS. The walls are madeof a double layer of 0.4 m thick magnetite-concrete blockswith a density of 3.9 ton/m3 to prevent ionizing radiationin the public areas around the bunker. Of the two smallerbunkers, 4 m by 2.7 m internal dimensions, one will beequipped with a 14 MeV neutron generator, based on DT-reactions with a flux of 1010 neutrons/second, for instrumentdevelopment and educational purposes. The second bunkeris available for future experiment proposals.

MAIN PROJECTS

At present the main projects in the FREIA Laboratory arecentered around the delopment of the ESS accelerator whilea THz-FEL study has been started for the longer term future.Among the critical elements of the ESS proton acceleratorare the superconducting accelerating cavities and their RFpower stations. FREIA is concentrating on the spoke linacpart of the accelerator and specificly on the developmentof the RF power station and high power test of the spokeresonators.

RF Power Station Development

A study has been done to investigate the technology choicefor the spoke RF power stations. Considering the requiredRF power levels, reliability and availability in time for theFREIA test stand and ESS construction, a choice was madefor tetrode vacuum tube amplifiers. The final choice wasmade for a TH595 type tetrode that can provide 200 kWpeak power at 5% duty cycle [4]. A set of two tetrodes withindividual solid-state pre-amplifiers is combined in a singleRF power station, see Figure 3.

The FREIA RF power stations are prototypes and pre-series for the ESS accelerator. After experience from thefirst RF power station has been gained during operation withsuperconducting spoke cavities, the design will be furtheroptimized for use at ESS before ordering the second RFpower station.


THPRO0773060

Cont

entf

rom

this

wor

km

aybe

used

unde

rthe

term

soft

heCC

BY3.

0lic

ence

(©20

14).

Any

distr

ibut

ion

ofth

isw

ork

mus

tmai

ntai

nat

tribu

tion

toth

eau

thor

(s),

title

ofth

ew

ork,

publ

isher

,and

DO

I.


Solid-state Amplifier and Combiner Development

In view of the increasing capabilities of solid-state transis-tors, we are working in-house to enhance the developmentof the technology for solid-state based RF power stations.We are optimizing the design of single transistor amplifiermodules [5] and in addition developing methods for the RFpower combination at the tens to hundreds of kW level [6].

With industry we are collaborating to develop and test acomplete 352 MHz 400 kW peak solid-state based RF powerstation compatible with the needs for the ESS spoke linac.This includes volume size limitations which are importantdue to the need to install 26 RF power stations in the ESS RFgallery. A prototype station is being developed by industrybased on commercial transistors with 1 kW peak poweroutput and a three level RF power combination scheme.

Spoke Cavity and Cryomodule Development

The ESS accelerator will contain 26 double spoke res-onators which are being developed by IPN Orsay [7]. Theprototype spoke resonators will be tested first at the SupraT-ech vertical test stand at IPN Orsay. One resonator will bebrought to FREIA where it will be tested in HNOSS. Firstat low power with a high-Q antenna to replicate verticaltest stand results, then fully dressed with the high powercoupler and tuning systems at nominal power. This testingprogramme will start towards the end of 2014.

The spoke resonators will be housed in pairs inside thespoke cryomodules also developed by IPN Orsay [8]. FREIAwill test the prototype spoke cryomodule and valve box atnominal RF power. Both spoke resonators of the cryomod-ule will be powered simultaneously to investigate any crosstalk, hence the need for multiple RF power stations. Fig-ure 4 shows the installation of HNOSS and a cryomodule atFREIA.

Having the facilities and experience for the prototypespoke cryomodule testing, it is planned that the series spokecryomodules for the ESS accelerator also will be tested atFREIA.

Accelerator and Test Stand Controls

Both FREIA and ESS have the need to develop controlsystems for their test stands and for the ESS accelerator.

HNOSS

horizontal test

cryostat

ESS

spoke

cryomodule

RF

power stations

cold helium

gas heater

Figure 4: Layout of the spoke cavities test stand.

The FREIA controls are based on the EPICS standards withindustrial PLCs, PXI and cRIO systems on the hardwareside. The system will be adapted to be compatible with thedeveloping software and hardware standards for the ESSIntegrated Control System. This provides an early test bedfor the ESS controls and offers the possibility to copy partsof the FREIA controls to the future ESS test stand and ac-celerator.

THz-FEL Development

The development and construction of the ESS spoke linacshall be completed by 2019. The FREIA facilities could thenbe used to accommodate a small CW electron acceleratorbased on two 352 MHz (spoke) superconducting acceleratorcavities. Such an accelerator could reach 15 MeV suffi-cient to power a THz-FEL in combination with an X-raysource. Powerful THz pulses can excite low-frequency vi-brations in biomolecules and induce charge carrier dynamicsin nanoscale structures. A preliminary conceptual designhas been studied [9] based on which a funding applicationhas been submitted for a full conceptual design study.

ACKNOWLEDGEMENTS

The authors wish to thank their partners ESS, IPN Or-say, CERN and Accelerator and Cryogenic Systems (ACS)for their advice, fruitful discussions and practical help indevelopment of the FREIA Laboratory and its equipment.This work is funded by the Knut and Alice Wallenberg Foun-dation, the Swedish Government, the Vice-chancellor ofUppsala University and ESS AB.

REFERENCES

[1] R. Santiago Kern et al., “The HNOSS horizontal cryostat andhelium liquefaction plant at FREIA”, IPAC 2014, WEPRI110.

[2] N.R. Chevalier et al., “Design of a horizontal test cryostat forsuperconducting RF cavities for the FREIA facility at UppsalaUniversity”, AIP Conf. Proc. 1574 (2014) 1277.

[3] R.A. Yogi et al., “Uppsala high power test stand for spokecavities”, Linac 2012, TUPB108.

[4] R.A. Yogi et al., “Tetrode based technology demonstrator at352 MHz, 400 kWp for ESS spoke linac”, IVEC 2014.

[5] D. Dancila et al., “Solid-state amplifier development atFREIA”, IPAC 2014, WEPME012.

[6] V.A. Goryashko et al., “A high power RF combiner for solid-state drivers”, IPAC 2014, WEPME013.

[7] P. Duchesne et al., “Design of the 352 MHz, Beta 0.50, double-spoke cavity for ESS”, SRF 2013, FRIOC01.

[8] D. Reynet et al., “Design of the ESS spoke cryomodule”, SRF2013, FRIOC01.

[9] V.A. Goryashko and V. Zhaunerchyk, “Conceptual Designof an Stockholm-Uppsala THz FEL Oscillator: report I ofthe series of reports by the Swedish FEL Center”, UppsalaUniversity, FREIA report 2013/04 (2013).



THPRO0773061

Cont

entf

rom

this

wor

km

aybe

used

unde

rthe

term

soft

heCC

BY3.

0lic

ence

(©20

14).

Any

distr

ibut

ion

ofth

isw

ork

mus

tmai

ntai

nat

tribu

tion

toth

eau

thor

(s),

title

ofth

ew

ork,

publ

isher

,and

DO

I.

the new freia laboratory for accelerator...

Documents