the 3 mev h - test stand at cern - the first part of the spl - h. haseroth

H. HaserothJuly 26 – August 1, 2004 NuFact04, Osaka

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The 3 MeV H- Test Stand at CERN

- The first part of the SPL -

H. Haseroth

on behalf of the SPL Study Group

(Prepared by Carlo Rossi)


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The 3 MeV H- Test Stand at CERN

OUTLINE

• The long term SPL project: motivation for a 3 MeV Test Stand.

• The intermediate Linac4 phase: a valuable improvement of the CERN proton accelerator complex.

• The 3 MeV Test Stand: a short term study tool and the future SPL Front End.

• Status and Planning.


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SPL: a long term project

A multi-MW superconducting linac could simultaneously satisfy the needs of many users. Especially relevant are the potential applications* for:

Radio-active ionsNeutrinos: super-beam/beta-beam/neutrino factoryLHC: potential to increase the brightness and intensity beyond the ultimate beam.

The challenge for high beam power is mostly coming from the control of beam halo. The control starts from the low energy end. A test bench for beam dynamics studies (including beam halo) is a must.

*Debated at the workshop on “Physics with a multiMW Proton Source”, CERN, May 25-27, http://physicsatmwatt.web.cern.ch/physicsatmwatt/


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SPL block diagram (CDR 1)

Linac 4: up-to-date designSuperconducting linac: CDR 1


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Linac4: a mid-term phase

Linac4 is the room-temperature section of the SPL (extended to 160 MeV), intended to upgrade the injection into the PS Booster.It allows for a significant performance improvement for the present users like LHC and ISOLDE, at a limited cost.

Standardoperation

Linac 4Basic user’s

request

CNGS flux [1019 pot/year] 4.7 (4.5) 7.5 (4.5) 4.5

FT spills [105 /year] 3.2 (3.4) 3.3 (5.6) 7.2

East Hall spills [106 /year] 1.5 1.5 1.3

NTOF flux [1019 pot/year] 1.6 1.6 1.5

ISOLDE flux [μA][nb. of pulses/hour]

3.12200

6.42240

1.91350

72 bunch train for LHC at PS exit [1011 ppb]

1.5 2 1.3 (2*)


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Linac4 parameters

•Relaxed parameters•Space and infrastructure available in the PS South Hall•RF from LEP (klystrons, waveguides, etc. - already in stock)

Linac4 could be later used as front-end of the SPL: its RF structures are designed to operate at the full SPL duty cycle. PARAMETERS Phase 1

(PSB)Phase 2 (SPL)

Maximum repetition rate 2 50 Hz

Source current * 50 30 mA

RFQ current * 40 21 mA

Chopper beam-on factor 75 62 %

Current after chopper * 30 13 mA

Pulse length (max.) 0.5 2.8 ms

Average current 15 1820 A

Max. beam duty cycle 0.1 14 %

Max. number of particles per pulse 0.9 2.3 · 1014

Transverse norm. emittance (rms) 0.25 0.25 mm mrad

Longitudinal emittance (rms) 0.3 0.3 deg MeV

Maximum design current 30 A


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DTL CCDTL SCL

3MeV 40MeV 90MeV 160MeV

Drift TubeLinac352 MHz16.7 m3 tanks5 klystrons

Side Coupled Linac704 MHz28.1 m20 tanks5 klystrons

Cell-Coupled Drift Tube L.352 MHz30.1 m33 tanks6 klystrons

Total Linac4: 86.5 m , 17 klystrons

30 mA, 0.1% duty

MEBTRFQH-

95keV

choppingline 3.6 m

IPHIRFQ6 m1 klystron

Final Energy 160 MeV,factor 2 in 2 w.r.t. present 50 MeV Linac2

Linac4 layout


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Installation Layout

3 MeVTest Place


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The 3 MeV Test Stand

H- ECR ion source

HV pulsed power supplies for the LEP klystrons

Specific ComponentsChopper structure

Bunching cavities

Beam Shape and Halo Monitor

IPHI RFQ


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The 3 MeV Test Stand

•Beam dynamics at low energy.•Development of the Chopper line:

– to generate the required time structure of the beam

– to clean the beam from halo

– to match it to the subsequent RF structures.


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The H- ECR Source

Tests on the prototype source are under way. Design work will be carried out during the rest of 2004 and 2005.The final source is not expected before 2007.


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The RFQ

The IPHI (“Injecteur de Protons de Haute Intensité”) RFQ is at the core of the 3 MeV Test Place. It is being developed in France within the IPHI collaboration between CEA and CNRS which CERN has recently joined .

RF power is generated by a LEP klystron (352.21 MHz, 1 MW CW) that will be operated in pulsed mode, by means of dedicated power supplies expressly developed by a collaboration between GSI and CERN.


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HV Pulsed Power Supplies for the LEP klystron

CERN and GSI are formalizing an agreement for the development of the power supplies based on common requirements (Linac4 @ CERN and FAIR injector @ GSI).Parameter Specified value

High Voltage pulse amplitude

-100 kV

High Voltage pulse width 700 s

Pulse repetition rate 5 Hz

Acceptable voltage deviation incl. ripple & drop

less than 0.1 % (peak to peak)

First power supply to be delivered before end 2005, second before end 2006.


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The Chopper line

General guidelines

Compact design3 m lengthDynamic range20 – 60 mASmall growth z = const

rout = 1.17 rin

Tolerant to alignment errorsGood vacuum ~10-8 Torr


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Beam Dynamics in the Chopper Line

The chopper line is designed transversely as five FODO periods, while longitudinally three RF cavities match the beam from the RFQ output to the (future) DTL input.

Bunchercavity

Bunchercavity

Bunchercavity

Chopperstructure

Chopperstructure

RFQoutput

DTLinput


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Beam Chopping (1)

Chopper Line Losses

Output 1st Buncher 0.08 % Input 1st Chopper 0.52 % Chopper Structure 0.63 % Chopped beam dump 4.44 %

0

10

20

30

40

50

60

70

80

90

100

110

2.5 2.55 2.6 2.65 2.7 2.75 2.8 2.85 2.9 2.95 3

Length [m]

Tra

nsm

issi

on

[%

]

Beam

Chopped Beam

94.3 %

0.016 %

dump

A beam dump has been designed to intercept the deviated beam 1 m downstream from the last chopper structure (radial separation between the beam centers: 1.5 cm)

3 bunchesare dumped

5 bunchesare transmitted

Beam Dump – Side view

= 10 degrees

Un-chopped beam

~ 100 mm

Water

Water

Vacuum

flange


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Beam Chopping (2)

2 ns rise/fall time is required for bunch selectivity (352 MHz beam structure), ±500V between the deflecting plates to get the required separation at the dump.

Double meander structure on Alumina substrate

The first chopper structure is under fabrication

The prototype of the RF amplifier is under test

Pulse length: 8ns to 2sRep. rate (max): 45 MHz


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Longitudinal matching

The longitudinal matching is performed by 3 RF cavities working at 352 MHz: two with 30 mm aperture (B30), and one with 40 mm aperture (B40) placed in the chopping region.

B30 B40Frequency (MHz) 352.0 352.0Gap length (mm) 14.0 14.0Q value 25000 24000Shunt impedance (M) 1.28 0.64R/Q 52.2 27.1Nominal voltage (kV) 140 100Dissipated power (kW peak) 1616.2Kilpatrick factor 1.22 1.16

The electromagnetic and mechanical design has been completed for the whole set of RF cavities. The construction phase for the first B30 cavity is starting and will be completed within the end of 2004.


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The Beam Shape & Halo Monitor

Longitudinal measurementMeasure residual H- in (not completely) chopped buckets with a sensitivity of ~ 1000 ions, in the vicinity of full bunches (108 ions). Detector must be turned ON/OFF within 1 ns, gating ratio 1:106

Transverse measurementHalo diagnostics: Beam core: d=1 cm, 108 H- /bunch/ cm2

Beam halo: d=4 cm, 103 H- /bunch/ cm2

Active area of detector 4 × 4 cmDynamic range: 1:106 by integrating over

several buckets

All components have been delivered. The vacuum chamber is being designed. The detector will be commissioned during the first months of 2005.


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Measurement Program

The 3 MeV test place will be used to commission the different components of the line and perform “conventional” measurements on the beam, in order to scan the full dynamic range of the system.Three sets of measurements have particular

relevance:Validation of the Chopper principle and hardwareCharacterize the separation capability (on/off) of the chopper line (chopper voltage) and its time selectivity (rise and fall time).Beam matching properties of the lineMeasure longitudinal and transverse emittance (expected accuracy within 10%) within different beam conditions.

Halo studiesOptimize the collimation system by characterizing the beam halo in shape and intensity.


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Planning of the Project

Linac4approval

Decisionon SPL

Test of Linac4 RF

structures is possible


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Status of the Project

• The European Union is supporting beam dynamics studies and RF system developments in the frame of the HIPPI “Joint Research Activity”.

• The design of the 3 MeV Test Stand is almost completed. Still missing:– study of the beam current monitor– design of the vacuum chamber (short sections between

major components)

• The design of the major components will be completed in 2004.

• The start of Linac4 construction in 2006 has been included by the CERN DG among the strategic priorities of the laboratory The 3 MeV Test Stand is being designed to become the Linac4 Front End.


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The full picture …

Linac4approval

SPLapproval

LHCupgrade

RF test place ready

3 MeV test place ready

CDR 2


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Thank you

and Carlo Rossi for the preparation

of this presentation

the 3 mev h - test stand at cern - the first part of the spl - h. haseroth

Documents

mev h test stand

mev test place

rf power

mev test standbeam dynamics

high beam power

test bench

dedicated power supplies

power supply