Neutrino Beam Design Considerations Stephen Kahn Brookhaven National Laboratory

March 3, 2004 S. Kahn

AGS Long Baseline Neutrino Beam

Neutrino Beam Design Considerations

Stephen Kahn Brookhaven National Laboratory

Presented to the

BNLMarch 3, 2004

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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



BNL Homestake Long Baseline Neutrino Beam

2540 km

Homestake BNL

•28 GeV protons from the AGS

•1 MW beam power from upgraded proton driver

•500 kTon Water Cherenkov Detector

•Conventional Horn Focused beam

Baseline Design:

•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.



The Wide Band Neutrino spectrum from the AGS

Proton energy 28 GeV 1 MW total power ~10

14 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 /m2/POT 52000 CC events during 5107 sec. 17000 NC events during 5107 sec.



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 5107 sec.

There is a significantly larger contamination in the

spectrum



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



Advantages of a Very Long Baseline

DISAPPEARANCE

0

50

100

150

200

250

0 1 2 3 4 5 6 7 8 9 10

Reconstructed Energy (GeV)

BNL-HS 2540 km

sin2223 = 1.0

m2 32 = 2.5e-3 eV2

1 MW, 0.5 MT, 5e7 sec

No oscillations: 13290 evts

With oscillations: 6538 evts

Background: 1211 evts

neutrino oscillations result from

the factor sin2(m322 L / 4E)

modulating the flux for each

flavor (here 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

m322 to be precisely measured

by a wavelength rather than an amplitude (reducing systematic errors)



Very Long Baseline Neutrino – m322 Nodes

neutrino node pattern is key to high-resolution m2 measurements

Fermi momentum sets E>1 GeV/c to maintain energy resolution

the distance scale is set by m23

2

BNL-HS 2540 km FNAL-HS 1290 km BNL-WIPP 2880 km BNL-Henderson 2770



BNL-AGS Target Power Upgrade to 1 MW

AGS is currently the highest intensity machine. Simple plan. Run the AGS faster. 2.5 HzNeed new LINAC @ 1.2 GeV to provide protons.Cost $265M FY03 (TEC) dollars.Energy is 28 GeV. 2.5 Hz operation is 1 MW



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



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



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.



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



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



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.

Parameter Value Distance from Target 285 m Depth Below Ground 21 m

Enclosure Length 15 m Enclosure Height above Floor 5 m

Enclosure Width 6 m (?)



AGS 1 MW Upgrade and SC Linac Parameters

Proton Driver Parameters

Item Value

Total beam power 1 MWProtons per bunch 0.41013

Beam energy 28 GeVInjection turns 230Average beam current 38 mARepetition rate 2.5 HzCycle time 400 msPulse length 0.72 msNumber of protons per fill 9.6 1013

Chopping rate 0.75Number of bunches per fill 24Linac average/peak current 20/30 mA

Superconducting Linac Parameters

Linac Section LE ME HE

Av Beam Pwr, kW 7.14 14.0 14.0Av Beam Curr, mA 35.7 35.7 35.7K.E. Gain, MeV 200 400 400Frequency, MHz 805 1610 1610Total Length, m 37.82 41.40 38.32Accel Grad, MeV/m 10.8 23.5 23.4norm rms , mm-mr 2.0 2.0 2.0



1 MW Target for AGS Super Neutrino Beam

1.0 MW He gas-cooled, Carbon-Carbon target for the Super Neutrino Beam



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 T840 °C

Parameter Value

Target Material Carbon-Carbon CompositeTarget 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

•The target is 1.5 interaction lengths long.



The Target and Horn Enclosure

Parameter Value Material Aluminum

Horn Current 250 kA Horn 1 Inner Radius 7 mm

Horn 1 Inner Conductor Thickness 2.5 mm Horn 1 Length 217 cm

Horn 1 Inductance 779 nH Horn 1 Resistance 248

Horn 2 Inner Radius 58.4 mm Horn 2 Inner Conductor Thickness 1.6 mm

Horn 2 Length 150 cm Horn 2 Inductance 287 nH Horn 2 Resistance 30

Stripline Inductance 480 mH Stripline Resistance 30

Pulse Width 1.2 ms Repetition Rate 2.5 Hz

Distance Betw. Horn Fronts Plates 8.17 m



Power Supply Issues



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.



BLIP Irradiation Studies

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

Thermal expansion of Super-Invar as a function of atom displacements



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



Summary

Technically feasible R&D items Cost is manageable

Neutrino Beam Design Considerations Stephen Kahn Brookhaven National Laboratory

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