THE DESIGN OF THE AGS-BASED PROTON DRIVER FOR NEUTRINO FACTORY W.T. WENG, BNL FFAG WORKSHOP JULY 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 ppy (10 7 sec) 4. Muon ~ 5 x mpy (10 7 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

6 12:00 o’clock 2:00 o’clock 4:00 o’clock 6:00 o’clock 8:00 o’clock PHOBOS 10:00 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  protons/pulse Injector to RHIC: < 2 hours about every 10 hours

7 AGS Intensity History 1 MW AGS

8 Total Accelerated Protons at the AGS 0.8     Total accelerated protons 1.0   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 Source plus RFQ Superconducting Linacs To RHIC 400 MeV 800 MeV 1.2 GeV To Target Station AGS 1.2 GeV  28 GeV 0.4 s cycle time (2.5 Hz) 0.2 s 200 MeV l 1.2 GeV superconducting linac extension for direct injection of ~ 1  protons low beam loss at injection; high repetition rate possible further upgrade to 1.5 GeV and 2  protons per pulse possible (x 2) l 2.5 Hz AGS repetition rate triple existing main magnet power supply and magnet current feeds double rf power and accelerating gradient further upgrade to 5 Hz possible (x 2)

11 AGS Proton Driver Parameters

GeV Superconducting Linac

13 SCL Layout

14 Injector and AGS Parameters for 1-MW Upgrade

15 A Cryo-Module

16 General Parameters of SCL Sections

GeV Superconducting Linac

18 AGS Booster PSR LANL SNS 1 MW AGS Beam power, Linac exit, kW Kinetic Energy, MeV Number of Protons N P, Vertical Acceptance A,   m  2  N P /  2  3 A),   m Total Beam Losses, % Total Loss Power, W  1440 Circumference, m Loss Power per Meter, W/m Beam Loss at H - Injection Energy

19 AGS Injection Simulation Injection parameters: Injection turns360 Repetition rate2.5 Hz Pulse length1.08 ms Chopping rate0.65 Linac average/peak current20 / 30 mA Momentum spread  0.15 % Inj. beam emittance (95 %)   m RF voltage450 kV Bunch length85 ns Longitudinal emittance1.2 eVs Momentum spread  0.48 % Circ. beam emittance (95 %) 100  m

20 Calculated Halo/Tail of the AGS Beam

21 New AGS Main Magnet Power Supply presently: –Repetition rate2.5 Hz1 Hz –Peak power110 MW 50 MW –Average power4 MW 4 MW –Peak current5 kA 5 kA –Peak total voltage  25 kV  10 kV –Number of power converters / feeds62

22 Eddy Current Losses in AGS Magnets For 2.5 (5.0) Hz: In pipe: 65 (260) W/m In 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/turn0.8 MV0.4 MV harmonic number Rf frequency~ 9 MHz MHz Rf peak power2 MW Rf magnetic field18 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 seems feasible for 1 MW, 28 GeV proton beam. Thin low Z target minimizes reabsorption 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 IIUpgrade III Linac intensity/pulse 1.0    Linac rep. rate 2.5 Hz 2.5 Hz 5.0 Hz Linac extraction energy 1.2 GeV 1.5 GeV 1.5 GeV  2  Beam power 54 kW 144 kW 288 kW AGS intensity/pulse 0.9    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 Source plus RFQ Superconducting Linacs To RHIC 400 MeV 800 MeV 1.5 GeV To Target Station AGS 1.2 GeV  28 GeV 0.2 s cycle time (5 Hz) 0.1 s 200 MeV

30 AGS Post-Accelerator (A. Ruggiero)

31 Characteristics of FFAG Accelerator 1.Fixed-field (no ramping), hence good for high repetition rate application. 2.Large momentum acceptance. 3.Limited energy gain, Pf / Pi  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.