THE DESIGN OF THE AGS-BASED PROTON

DRIVER FOR NEUTRINO FACTORY

W.T. WENG, BNL

FFAG WORKSHOPJULY 7-11, 2003

KEK, JAPAN

2

OUTLINES

1. Introduction

2. Performance Challenges

3. Superconducting Linac

4. 1 MW AGS upgrade

5. Ways to 4 MW

6. Possible Application of FFAG

3

REQUIREMENT FOR A PROTON DRIVER

1. Energy 20 to 50 GeV

2. Power ~ 4 MW

3. Proton ~ 10 x 1021 ppy (107 sec)

4. Muon ~ 5 x 1021 mpy (107 sec)

5. Reliability ~ 85%

4

PERFORMANCE CHALLENGES

a. Space Charge Effect

b. Coherent Instabilities

c. Injection and Extraction

d. Beam Loss and Collimation

e. Target and Horn

f. Reliability

5

High Intensity Proton Sources for Neutrino Experiments

Machine Flux

(1013/pulse)

RepRate(Hz)

Flux(1020/year)

Ep(GeV)

Power(MW)

Eυ(GeV)

L(Km)

Detector

Existing and Approved KEK PS 0.8 0.5 0.4 12 0.005 1.3 250 SK

Fermilab Booster 0.5 7.5 3.8 8 0.05 0.7 0.5 Mini BooneFermilab Main Injector 3 0.54 1.6 120 0.4 3.5 730 MINOS

CERN SPS 4.8 0.17 0.8 400 0.5 17 732 ICARUSOPERA

JHF 50 GeV 32 0.3 10 50 0.75 0.8 295 SKProposed Facilities

Fermilab MI Upgrade 15 0.65 9.8 120 1.9 3.5 730 MINOS

BNL AGS Upgrade 9 2.5 25 28 11.0-7.0 2540

"UNO" or3M

JHF Upgrade 32 0.9 30 50 2.2 0.8 295 HKCERN SPL 23 50 1100 2.2 4 0.26 130

6

12:00 o’clock

2:00 o’clock

4:00 o’clock6:00 o’clock

8:00 o’clock

PHOBOS10:00 o’clock

BRAHMS & PP2PP (p)

STAR (p)PHENIX (p)

RHIC

AGS

LINAC

BOOSTER

TANDEMS

BAF (NASA) g-2

HEP/NP

U-line

AGS/RHIC Accelerator Complex

Pol. Proton Source

High Intensity Source

Slow extraction

Fast extraction AGS:Intensity: 7 1013 protons/pulseInjector to RHIC:< 2 hours about every 10 hours

7

AGS Intensity History

1 MW AGS

8

Total Accelerated Protons at the AGSAGS Accelerated Protons 1/1/1993 to 9/30/2002

0.0E+00

2.0E+19

4.0E+19

6.0E+19

8.0E+19

1.0E+20

1.2E+20

Jan

-93

Jan

-94

Jan

-95

Jan

-96

Jan

-97

Jan

-98

Jan

-99

Jan

-00

Jan

-01

Jan

-02

date

acce

lera

ted

pro

ton

s (

red

= S

EB

, b

lue

= F

EB

)

0.8 1020

0.6 1020

0.4 1020

0.2 1020

0

Tot

al a

ccel

erat

ed p

roto

ns 1.0 1020

1.2 1020

Slow extracted beam (Kaon decay) Fast extracted beam (g-2)Note: Lower total accelerated protons in later years due to much shorter running time

9

AGS Upgrade for Neutrino Factory

A. 1.2 GeV Superconducting Linac

B. AGS Upgrade to 1 MW:

Beam loss considerations

1.2 GeV Superconducting Linac

2.5 Hz AGS power supply and rf system

Neutrino beam production

C. AGS upgrade to 4MW

10

AGS Upgrade to 1 MW

200 MeV Drift Tube Linac

BOOSTER

High Intensity Sourceplus RFQ

Superconducting Linacs

To RHIC

400 MeV

800 MeV

1.2 GeV

To Target Station

AGS1.2 GeV 28 GeV

0.4 s cycle time (2.5 Hz)

0.2 s 0.2 s

200 MeV

1.2 GeV superconducting linac extension for direct injection of ~ 1 1014 protonslow beam loss at injection; high repetition rate possiblefurther upgrade to 1.5 GeV and 2 1014 protons per pulse possible (x 2)

2.5 Hz AGS repetition ratetriple existing main magnet power supply and magnet current feedsdouble rf power and accelerating gradientfurther upgrade to 5 Hz possible (x 2)

11

AGS Proton Driver Parameters

Present 1 MW 4 MWAGS AGS AGS J-PARC

Total beam power [MW] 0.14 1.00 4.00 0.75Beam energy [GeV] 24 28 28 50Average current [A] 6 36 144 15Cycle time [s] 2 0.4 0.2 3.4No. of protons per fill 0.7 1014 0.9 1014 1.8 1014 3.3 1014

Average circulating current [A] 4.2 5.0 10 12No. of bunches at extraction 6 24 24 8No. of protons per bunch 1 1013 0.4 1013 0.8 1013 4 1013

No. of protons per 107 sec. 3.5 1020 23 1020 90 1020 10 1020

12

1.2 GeV Superconducting Linac

Beam energy 0.2 0.4 GeV 0.4 0.8 GeV 0.8 1.2 GeV Rf frequency 805 MHz 1610 MHz 1610 MHz Accelerating gradient 10.8 MeV/m 23.5 MeV/m 23.4 MeV/m Length 37.8 m 41.4 m 38.3 m Beam power, linac exit 17 kW 34 kW 50 kW

13

SCL Layout Medium

Front End Low-Energy Energy High-EnergyRT Linac Section Section Section

To the AGS

201.25 MHz 805 MHz 1,610 MHz 1,610 MHz

200 MeV 400 MeV 800 MeV 1.2 GeV

Front End Medium-Beta High-Beta DTL CCL Section Section To the SNS

402.5 MHz 805 M Hz 805 MHz 805 MHz

185.6 MeV 387 MeV 1.0 GeV

14

Injector and AGS Parameters for 1-MW Upgrade

Increm. Linac Ave. Power 37.5 kW Ion Source Current 100 mAKinetic Energy in exit 1.2 GeV RT Linac Transmis., % 30 0.8986 Chopping Ratio, % 75Momentum, GeV/c 1.92 Peak Current, mA 28Magnetic Rigidity, T-m 6.41 Average Current, mA 21Repetition Rate, Hz 2.5 Injection Loss, % 5.0Linac Average Current, µA 37.6 Injected Protons per Turn 3.74 x 1011

No. of Protons / pulse 9.38 x 1013 Number of Injected Turns 239AGS Circumference, m 807.076 Linac Pulse Length, ms 0.716Revol. Frequency, MHz 0.3338 Linac Duty Cycle, % 0.179Revolution Period, µs 2.996 Bunching Factor 4Bending Radius, m 85.378 Norm. Emitt., š mm- mrad 100Injection Field, kG 0.7507 Emittance, š m m-mrad 48.8Extraction Field, kG 11.30 Space-Charge 0.187RF at Inject. (h = 24), MHz 8.01 RF at Extr. (h = 24), MHz 8.91

15

A Cryo-ModuleLw = 30 cm

Couplers (70 cm)

One Coupler per Klystron per Cavity (same as in SNS)8 Cells per Cavity (6 in SNS)4 Cavities per (Cryo-)Module (3 in Medium- and 4 in High- SNS)

Cavity Separation = 6.4b (10b)

2b 2d

2b = 10 (8) cm 2d = 34 cm @ 805 MHz = 5 cm = 17 cm @ 1,610 MHz

16

General Parameters of SCL SectionsLinac Section LE ME HEAve. increm. Beam Power, kW 7.52 15.0 15.0Average Beam Current, µA 37.6 37.6 37.6Initial Kinetic Energy, MeV 200 400 800Final Kinetic Energy, MeV 400 800 1200Frequency, MHz 805 1610 1610No. of Protons / Bunch x 108 8.70 8.70 8.70Temperature, oK 2.1 2.1 2.1Cells / Cavity 8 8 8Cavities / Cryo-Module 4 4 4Cavity Separation, cm 32.0 16.0 16.0Cold-Warm Transition, cm 30 30 30Cavity Internal Diameter, cm 10 5 5Length of Warm Insertion, m 1.079 1.379 1.379Accelerating Gradient, MeV/m 10.5 22.9 22.8Ave. (real-estate) Gradient, MeV/m 5.29 9.44 10.01Cavities / Klystron 1 1 1No. of rf Couplers / Cavity 1 1 1Rf Phase Angle 30o 30o 30o

Method for Transverse Focussing FODO Doublets DoubletsBetatron Phase Advance / FODO cell 90o 90o 90o

Norm. rms Emittance, š m m-mrad 2.0 2.0 2.0Rms Bunch Area, š oMeV (805 MHz) 0.5 0.5 0.5

Medium- High-220 669

1092 1092185.6 387

387 1000805 8054.3 4.32.1 2.1

6 63 4

40.0 40.070 70

8 81.600 1.600

10.4 16.33.13 6.53

1 11 1

(30o) (30o)Doublets Doublets

90o 90o

(0.3) (0.3)(0.5) (0.5)

17

1.2 GeV Superconducting Linac

18

AGS Booster PSR LANL SNS 1 MW AGS

Beam power, Linac exit, kW 3 80 1000 50

Kinetic Energy, MeV 200 800 1000 1200

Number of Protons NP, 1012 15 31 100 100

Vertical Acceptance A, m 89 140 480 55

23 0.57 4.50 6.75 9.56

NP /23 A), 1012 m 0.296 0.049 0.031 0.190

Total Beam Losses, % 5 0.3 0.1 3

Total Loss Power, W 150 240 10001440

Circumference, m 202 90 248 807

Loss Power per Meter, W/m 0.8 2.7 4.0 1.8

Beam Loss at H- Injection Energy

19

AGS Injection Simulation•Injection parameters:•Injection turns 360•Repetition rate 2.5 Hz•Pulse length 1.08 ms•Chopping rate 0.65•Linac average/peak current 20 / 30 mA•Momentum spread 0.15 %•Inj. beam emittance (95 %)m

•RF voltage 450 kV•Bunch length 85 ns

•Longitudinal emittance 1.2 eVs•Momentum spread 0.48 %•Circ. beam emittance (95 %) 100m

20

Calculated Halo/Tail of the AGS Beam

21

New AGS Main Magnet Power Supplypresently:

– Repetition rate 2.5 Hz 1 Hz– Peak power 110 MW 50 MW– Average power 4 MW 4 MW– Peak current 5 kA 5 kA– Peak total voltage 25 kV 10 kV– Number of power converters / feeds 6 2

22

Eddy Current Losses in AGS Magnets

For 2.5 (5.0) Hz:In pipe: 65 (260) W/mIn coil: 225 (900) W/m

23

AGS RF System Upgrade

Use present cavities with upgraded power supplies (two 300 kW tetrodes/cavity)

presently:• Rf voltage/turn 0.8 MV 0.4 MV• harmonic number 24 6 - 12• Rf frequency ~ 9 MHz 3 - 4.5 MHz• Rf peak power 2 MW• Rf magnetic field 18 mT

24

Neutrino Beam Production

• 1 MW He gas-cooled Carbon-carbon target

• New horn design• Target on down-hill slope for

long baseline experiment• Beam dump well above ground

water table to avoid activation

25

Neutrino Spectrum at 1 km

Low Z (Carbon) target seemsfeasible for 1 MW, 28 GeV proton beam.

Thin low Z target minimizesreabsorption which increases flux of high energy neutrinos

26

Beam Line to Homestake Mine

Can be directed to any western direction.

W

27

Detector at Homestake

28

Path Towards 4 MW Upgrade I Upgrade II Upgrade III

• Linac intensity/pulse 1.0 1014 2.0 1014 2.0 1014

• Linac rep. rate 2.5 Hz 2.5 Hz 5.0 Hz• Linac extraction energy 1.2 GeV 1.5 GeV 1.5 GeV 23 9.6 14.9 14.9• Beam power 54 kW 144 kW 288 kW• AGS intensity/pulse 0.9 1014 1.8 1014 1.8 1014 • AGS rep. rate 2.5 Hz 2.5 Hz 5.0 Hz• Rf peak power 2 MW 4 MW 8 MW• Rf gap volts/turn 0.8 MV 0.8 MV 1.5 MV• AGS extraction energy 28 GeV 28 GeV 28 GeV• Beam power 1 MW 2 MW 4 MW

29

4 MW AGS Proton Driver Layout

200 MeV Drift Tube Linac

BOOSTER

High Intensity Sourceplus RFQ

Superconducting Linacs

To RHIC

400 MeV

800 MeV

1.5 GeV

To Target Station

AGS1.2 GeV 28 GeV

0.2 s cycle time (5 Hz)

0.1 s 0.1 s

200 MeV

30

Post Stretcher-Accelerator Ring

RT Linac AGS

SC Linac

AGS Post-Accelerator (A. Ruggiero)

Post Stretcher-Accelerator Ring Cycle 40 GeV – 16 kG

0.25 s

24 GeV – 10 kG

0.2 s 0.2 sAGS Cycle

GeV kG MW š mm mrad

1.2 0.75 -- 48.8324.0 9.74 0.86 3.7628.0 11.30 1.00 3.2435.0 14.04 1.25 2.6140.0 15.99 1.43 2.29

31

Characteristics of FFAG Accelerator1.Fixed-field (no ramping), hence good for

high repetition rate application.

2.Large momentum acceptance.

3.Limited energy gain, Pf/Pi 3.0.

4.Complicated longitudinal dynamics.

5.High intensity performance has not been demonstrated.

6.Difficulty in injection and extraction.

32

Possible Application of FFAG

1.Replacement of SCL for AGS Injection.

a. electron stripping precludes H- acceleration.

b. Need kHz rep. rate for FFAG for multi-batch injection.

2.Energy Doubler for SNS or ISIS is viable.

3.Replace LAR for either SNS or ESS.

a. need further work in high intensity acceleration and injection/extraction.

33

Possible Application of FFAG - Continued

4.May be good for APT.

5.May be good for RIA.

6.Electron Injector (low current, low energy, high rep. rate.

34

Conclusion

An upgraded AGS with 1 MW (further upgradeable to 4 MW) beam power is a cost effective proton driver for a neutrino superbeam for very long baseline experiments and eventually as a proton driver for neutrino factory.