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5  AGS Upgrade

The Alternating Gradient Synchrotron (AGS) at BNL is presently the world's highest intensity, multi-GeV proton accelerator and is a natural candidate for the proton driver needed to provide multi-megawatt proton beams (superbeams) for the next generation of neutrino oscillations research program in the U.S. Taking this qualitative fact to the next level, accelerator scientists at BNL have created a credible and effective plan for upgrade of the AGS to the 1 MW proton source needed by the neutrino program advocated in this paper. The increase is a factor of 6 from the present 0.17 MW beam power level. Furthermore, this plan could be time phased to evolve in stages from a 0.4 MW source available in a few years to an ultimate capability of up to 4 MW if such driver power is needed to complete the neutrino research program. At present, we believe a 1 MW source will be adequate for the foreseen program.

Our planned upgrade path would begin with the addition of a 1 GeV superconducting extension to the existing 200 MeV Cu LINAC that currently feeds the Booster ring. The resulting 1.2 GeV hybrid LINAC would bypass the Booster and inject directly into the AGS. The purpose here is to eliminate the need for six complete Booster cycles to fill the AGS and to inject all the needed 1.2 GeV protons in about 0.7 milliseconds. This step increases the average AGS power from 0.17 MW to 0.4 MW, enough to credibly begin the proposed neutrino oscillations program. By next adding new power supplies for the AGS ring, plus added RF power to rapidly accelerate the beam to 28 GeV, the AGS will be operational at the 1 MW power level. Further upgrades could increase the power level to as high as 4 MW if this becomes necessary.

We also note that the technical basis for the proposed upgrade has been documented in a recent study for a muon storage ring, "Feasibility Study-II of a Muon-Based Neutrino Source", June 14, 2001 [24]. Here we present a brief summary of the parameter lists for the required AGS upgrade, along with a summary of the direct costs that were derived in the muon storage ring study. The 1 MW requirements are summarized in Table 2 and a layout of the upgraded AGS is shown in Figure 37.

Table 2: AGS Proton Driver Parameters.
Total beam power 1 MW Protons per bunch 0.4× 1013
Beam energy 28 GeV Injection turns 230
Average beam current 42 ľA Repetition rate 2.5 Hz
Cycle time 400 ms Pulse length 0.72 ms
Number of protons per fill 9× 1013 Chopping rate 0.75
Number of bunches per fill 24 LINAC average/peak current 20/30 mA

Figure 37: AGS Proton Driver Layout.

5.1  Superconducting LINAC

The superconducting LINAC (SCL) accelerates the proton beam from 200 MeV to 1.2 GeV. The presented configuration follows a similar design described in detail in [27] and [28]. All three LINACs are built up from a sequence of identical periods. The major parameters of the three sections of the SCL are given in Table 3. The low energy section operates at 805 MHz and accelerates proton from 200 to 400 MeV. The following two sections, accelerating to 800 MeV and 1.2 GeV respectively, operate at 1.61 GHz. A higher frequency is desirable for obtaining a larger accelerating gradient with a more compact structure and reduced cost. The SCL will be operated at 2K for the assurance of reaching the desired gradient.


Table 3: General Parameters of the SCL.
LINAC Section LE ME HE
Average Beam Power, kW 7.14 14.0 14.0
Average Beam Current, ľA 35.7 35.7 35.7
Initial Kinetic Energy, MeV 200 400 800
Final Kinetic Energy, MeV 400 800 1200
Cell Reference β0 0.615 0.755 0.887
Frequency, MHz 805 1610 1610
Cells/Cavity 8 8 8
Cavities/Cryo-Module 4 4 4
Cavity Internal Diameter, cm 10 5 5
Total Length, m 37.82 41.40 38.32
Accelerating Gradient, MeV/m 10.8 23.5 23.4
Cavities/Klystron 1 1 1
Norm. rms Emittance, πmm-mrad 2.0 2.0 2.0
Rms Bunch Area, πoMeV (805 MHz) 0.5 0.5 0.5

5.2  Upgrade to 4 MW

The AGS-based neutrino superbeam can be further upgraded to 4 MW by: 1) increasing the LINAC energy to 1.5 GeV, 2) increasing the AGS intensity to 1.8× 1014 ppp, and 3) increasing the AGS rep rate to 5.0 Hz. The associated problems in beam dynamics, power supply, RF system, beam losses and radiation protection are under study and appear to be feasible if such a capability is required by the physics experiments.

5.3  Cost of the AGS upgrade

A preliminary cost of upgrading the accelerator complex to 1 MW is shown in Table 4. This upgrade could be done in phases if required by the funding plan. We are still in the process of creating a detailed staging plan.

Table 4: Preliminary direct costs of upgrading the AGS to 1 MW. These costs do not include EDIA, contingency, and overheads.


1.2 GeV Superconducting LINAC  
LE SC LINAC $36.1 M
ME SC LINAC $25.9 M
HE SC LINAC $28.2 M
AGS upgrades  
AGS Power Supply $32.0 M
AGS RF upgrade $8.6 M
AGS injection channel $ 3.7 M
Full turn extraction $ 5.5 M
Total $140 M

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