Neutrino Beam Design Considerations Stephen Kahn Brookhaven National Laboratory

1. Neutrino Beam Design Considerations Stephen Kahn Brookhaven National Laboratory Presented to the BNL March 3, 2004 S. Kahn AGS Long Baseline Neutrino Beam

2. Outline of talk Description and status of the proposed Deep Underground Science and Engineering Laboratory (DUSEL). Physics of a Very Long Baseline Neutrino Oscillation Experiment.  Status of VLBL experiment at Brookhaven National Laboratory. Opportunities for Long Term Collaboration. http://int.phys.washington.edu/NUSEL S. Kahn AGS Long Baseline Neutrino Beam

3. Homestake BNL 2540 km BNL  Homestake Long Baseline Neutrino Beam Baseline Design: • 28 GeV protons from the AGS • 1 MW beam power from upgraded proton driver • 500 kTon Water Cherenkov Detector • Conventional Horn Focused beam • Alternate detector technologies are being considered. • Alternate detector sites such as the WIPP facility in New Mexico and the molybdenum mines in Colorado would be acceptable. S. Kahn AGS Long Baseline Neutrino Beam

4. The Wide Band Neutrino spectrum from the AGS • Proton energy 28 GeV • 1 MW total power • ~1014 proton on target per pulse • Cycle at 2.5 Hz • Pulse width 2.5 s • Horn focused beam with graphite target • Flux at 1 km: 5x10-5 n/m2/POT • 52000 CC events during 5107 sec. • 17000 NC events during 5107 sec. S. Kahn AGS Long Baseline Neutrino Beam

5. Anti-neutrino Wide Band Spectrum from the AGS • 28 GeV proton energy with a 1 MW proton driver source. • 1014 protons per pulse cycled at 2.5 Hz • Horn focused beam with opposite current setting • We would expect ~60000 non-oscillating events at Homestake for  with a 2 MW power source in 5107 sec. • There is a significantly larger  contamination in the  spectrum S. Kahn AGS Long Baseline Neutrino Beam

6. 1 Degree Off-Axis Beam Option • The neutrino beamline can be designed with an option to run an off axis  beam. • The horn can be designed to be moved and oriented for a 1º off axis beam. • The decay tunnel would need a larger 4 m diameter. • The  spectrum shown has a narrower energy spread than the standard wide band beam. • The off-axis beam is significant for 0.5-3.0 GeV instead of 0.5-5.0 GeV for the wide-band beam. • The e/ ratio is significantly in the range where  is significant. BNL Off-axis Beam Option S. Kahn AGS Long Baseline Neutrino Beam

7. Advantages of a Very Long Baseline  neutrino oscillations result from the factor sin2(Dm322L / 4E) modulating the n flux for each flavor (here nm disappearance)  the oscillation period is directly proportional to distance and inversely proportional to energy  with a very long baseline actual oscillations are seen in the data as a function of energy  the multiple-node structure of the very long baseline allows the Dm322 to be precisely measured by a wavelength rather than an amplitude (reducing systematic errors) S. Kahn AGS Long Baseline Neutrino Beam

8. Very Long Baseline Neutrino – Dm322 Nodes • neutrino node pattern is key to high-resolution Dm2 measurements • Fermi momentum sets En>1 GeV/c to maintain n energy resolution • the distance scale is set by Dm232 • BNL-HS 2540 km • FNAL-HS 1290 km • BNL-WIPP 2880 km • BNL-Henderson 2770 S. Kahn AGS Long Baseline Neutrino Beam

9. BNL-AGS Target Power Upgrade to 1 MW AGS is currently the highest intensity machine. Simple plan. Run the AGS faster. 2.5 Hz Need new LINAC @ 1.2 GeV to provide protons. Cost $265M FY03 (TEC) dollars. Energy is 28 GeV. 2.5 Hz operation is 1 MW S. Kahn AGS Long Baseline Neutrino Beam

10. Super Neutrino Beam Geographical Layout  BNL can provide a 1 MW capable Super Neutrino Beam  the neutrino beam can aim at any site in the western U.S.; the Homestake Mine is shown here  there will be no environmental issues if the beam is produced atop the hill illustrated here and the beam dumped well above the local water table  construction of the Super Neutrino Beam is essentially de-coupled from AGS and RHIC operations S. Kahn AGS Long Baseline Neutrino Beam

11. 3-D Neutrino Super Beam Perspective • The  beamline is inclined 11.3º with respect to ground level to reach the Homestake mine • Shielding is removed in figure to see the beamline. • The hill is designed such that the target station, decay tunnel and beam dump are above the water table S. Kahn AGS Long Baseline Neutrino Beam

12. Elevation View of Beamline • The extracted beam from the AGS first follows the existing U-line. • It is bent upwards by 11º with a single 90º phase advance cell. • It is bent horizontally 68º with a 4 cell system having a 90º phase advance. • It is finally bent downward by 11.3º to aim at Homestake. • It is focused to a 2 mm radius on the target. • The top of the hill is 49 m above ground level. S. Kahn AGS Long Baseline Neutrino Beam

13. Alignment Issues – Criteria • We need to be able to establish the expected flux at the far detector to a precision to adequately perform the physics S. Kahn AGS Long Baseline Neutrino Beam

14. Radiation Safety and Shielding issues • Our current conceptual design for this proposed neutrino facility must meet and does meet all the necessary standards for radiation protection. • MCNPX calculations of radiation pattern near shielding • This includes chronic exposure in adjacent areas and offsite. • The design also prevents contamination of the ground water. 9 m of soil shielding over decay tunnel 9 m of Fe shielding for beam dump S. Kahn AGS Long Baseline Neutrino Beam

15. The Near Detector Station • The near detector facility will be located at 285 m from the target just after the beam stop. • This location is constrained by the steep incline of the beamline. • The near detector will not see the  beam as a point source. • Extracting flux information at the far detector will require an analysis similar to that to be used at JPARC. • The detector technology used for the close detector should be similar to that used at the far detector in order to minimize systematic errors. S. Kahn AGS Long Baseline Neutrino Beam

16. AGS 1 MW Upgrade and SC Linac Parameters Superconducting Linac Parameters Linac Section LE ME HE Av Beam Pwr, kW 7.14 14.0 14.0 Av Beam Curr, mA 35.7 35.7 35.7 K.E. Gain, MeV 200 400 400 Frequency, MHz 805 1610 1610 Total Length, m 37.82 41.40 38.32 Accel Grad, MeV/m 10.8 23.5 23.4 norm rms e, p mm-mr 2.0 2.0 2.0 Proton Driver Parameters Item Value Total beam power 1 MW Protons per bunch 0.41013 Beam energy 28 GeV Injection turns 230 Average beam current 38 mA Repetition rate 2.5 Hz Cycle time 400 ms Pulse length 0.72 ms Number of protons per fill 9.61013 Chopping rate 0.75 Number of bunches per fill 24 Linac average/peak current 20/30 mA S. Kahn AGS Long Baseline Neutrino Beam

17. 1 MW Target for AGS Super Neutrino Beam  1.0 MW He gas-cooled, Carbon-Carbon target for the Super Neutrino Beam S. Kahn AGS Long Baseline Neutrino Beam

18. Parameter Value Target Material Carbon-Carbon Composite Target Radius 6 mm Target Length 80 cm Horn Inner Radius 7 mm Horn Outer Radius 61 mm Horn Inner Conductor Thickness 2.5 mm Horn Length 217 cm Target Density 1.9 g/cm3 Target and Horn Design • The target is made of a carbon-carbon composite. • This is a 3D weaving of carbon fibers. • It is a low Z material. • It exhibits low thermal expansion up to 1000 C. • elongation< 0.04% in this range • Thermal shock to the target is greatly reduced. • It exhibits much greater structural strength than graphite. • The target will be cooled by convection from forced helium flow • The energy deposit in the target should be 7.3 kJ per pulse. • Including heat deposited in the horn from radiation and electro-thermal heating of the horn, we would like to remove 18.25 kJ per pulse. • Helium flowing at 40 m/s will keep the temperature to T840 °C • The target is 1.5 interaction lengths long. S. Kahn AGS Long Baseline Neutrino Beam

19. The Target and Horn Enclosure S. Kahn AGS Long Baseline Neutrino Beam

20. Power Supply Issues S. Kahn AGS Long Baseline Neutrino Beam

21. Target and Horn Material R&D • The materials choices for the target and horn of a 1+ MW system are challenging. • Must survive the heat generated from the beam. • The target must have minimum thermal-mechanical response to the beam. • Materials must survive irradiation and corrosion effects. • We have been examining new materials that can be used with proton sources with more than 1 MW. S. Kahn AGS Long Baseline Neutrino Beam

22. BLIP Irradiation Studies Thermal expansion of Super-Invar as a function of atom displacements • We are in the process of irradiating possible target materials in the BLIP facility at BNL. • The samples will receive exposures representative of the expected lifetime of the neutrino facility. • Target materials that will be examined (in the next few weeks) are • Carbon-Carbon Composite • Titanium Ti-6 Al-4V alloy • Toyota Gum Metal • High strength, near-zero expansion coefficient • Vascomax • AlBeMet • Aluminum-Beryllium alloy. • Horn material • Nickel-plated T6062 Aluminum that is being used in the NuMI horn S. Kahn AGS Long Baseline Neutrino Beam

23. Estimated Costs and Schedules of the Proposed Neutrino Facility • These are preliminary total estimated costs (TEC) in FY03 dollars including • EDIA (15%) • Contingency (30%) • BNL overhead S. Kahn AGS Long Baseline Neutrino Beam

24. Summary • Technically feasible • R&D items • Cost is manageable S. Kahn AGS Long Baseline Neutrino Beam