NuMI Hadron and Muon Monitoring
Fermilab

UWisconsin

Robert Zwaska
University of Texas at Austin
NBI 2003
November 10, 2003

UTexas -- Austin

System Geographyπ+Alcove 1

Alcove 2

Alcove 3υµµ+••Hadron Monitor
Max fluxes 109/cm2/spill
Rad levels ~2 × 109 Rad/yr.

November 10, 2003••

Muon Monitors
Max fluxes 4 107/cm2/spill
Rad levels ~ 107 Rad/yr.

Robert Zwaska
NBI 2003

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3.0
2.5
2.0
1.5
1.0

Muons / cm2 / spill

109 Particles / cm2 / spill

Particle Fluences
107

Alcove 1
Alcove 2
Alcove 3

1060.50.0Radius (cm)• Neutron fluences are ~ 10× that of charged particles atHadron Monitor & Alcove 1 locations• Hadron Monitor insensitive to horn focusing• Muon Monitor distributions flat
November 10, 2003

Robert Zwaska
NBI 2003

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Role of Monitors• Commissioning the beam – check of alignment¾Proton beam – Hadron Monitor¾Neutrino beam – Muon Monitor• Normal beam operations – ensure optimal beam
¾Proton beam angle – Hadron Monitor¾Target integrity – Hadron Monitor¾Horn integrity, position – muon monitor• Re-commissioning the beam if optics moved

November 10, 2003

Robert Zwaska
NBI 2003

4

Information in Alcoves12• Hadron Monitor swamped by π’s, protons, e+e−
• Alcoves have sharp cutoff energies• Even Alcove 1 doesn’t see softest parents
November 10, 2003

Robert Zwaska
NBI 2003

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Flexible Energy Beam
• Low Eν beam flat, hard to monitor
relevant parent particles.
• Best way to focus higher energy
pions: focus smaller angles.
• Place target on rail system
for remote motion capability.

M. Kostin, S. Kopp, M. Messier,D. Harris, J. Hylen, A. ParaTarget

0.35 – 3.96 m
10 m
November 10, 2003

Robert Zwaska
NBI 2003

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Variable Beam as Monitoring Tool• Muon alcoves have narrow acceptance (long decaytube!)• As Eν increased, decay products boosted forward• See peak in particle fluxes as energy increases• Use variablebeam asperiodicmonitoring
diagnostic

1
2
3-D. Harris
November 10, 2003

Robert Zwaska
NBI 2003

7Muon Monitors
12• Alignment of ν beam
¾ Beam center to ~ few cm¾ Lever arm is 740, 750, 770 m¾ ν beam direction to ~ 100 µrad
¾ Can measure in 1 beam spill¾ Requires special ME/HE running• As beam monitor¾Rates sensitive to targeting¾Centroid sensitive to horn focusing¾Centroid requires ME/HE run(1 spill)

November 10, 2003

Robert Zwaska
NBI 2003

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Parallel Plate Ion Chambers
11.4 × 11.4 cm2 Al2O3 ceramic wafers
Ag-plated Pt electrodes
Similar HV ceramic wafer
Holes in corners for mounting
Vias to solder pads on reverse side.
Separate mechanical support andelectrical contacts• Adopt design with electrical &mechanical contacts in corner holes
Chamber gap depends on station• Ionization medium: Helium gas atatmospheric pressure••••••

Sense wafer, chamber side

November 10, 2003

Robert Zwaska
NBI 2003

9Booster Beam Test
Fermilab Booster Accelerator
8 GeV proton beam
5×109 - 5×1012 protons/spill
5 cm2 beam spot size
10 November 2001

• Two chambers tested (1mm& 2mm gas gap)
• 2 PCB segmented ionchambers for beam profile.
• Toroid for beam intensity

High-Intensity Beam Test
Fermilab Booster

R. Zwaska et al., IEEE Trans.
Nucl. Sci. 50, 1129 (2003)

8 GeV proton beam
5×109 - 5×1012 protons/spill
5 cm2 beam spot size
1mm and 2mm chamber gaps tested• See onset of charge loss at
4×1010 protons/cm2/spill.
• Effect of recombination as chamberfield is screened by ionization.

Simulating a Chamber
1 mm separation
200 V applied
1.56 µs spill¾Predict Behavior seen in beam test
¾1 Dim. finite element model incorporating:¾Charge Transport¾Space Charge Build-Up & Dead Zone
¾Gas Amplification
3x Applied Field!
¾Recombination

1E11

1E10

Dead Zone

Simulate Multiplication and Recombination
dn¾Use the same volume recombination: dt = −kn n+ −dN= Nα¾Include gas multiplication:dx⎡
B ⎤⎢⎥= Aexp −⎣ (E / P) ⎦P

α¾Space Charge creates an electric field larger than the applied fieldData⇔

Simulation

UpturnPlateau Curves¾Curves converge in a region of voltage near a gain of 1
¾Data suggests 15-20 electron-ion pairs / cmData⇔

Simulation
Crossing point moves
with multiplication

More Mult.
←→Less Mult.

Neutron Backgrounds• Neutron Fluxes are comparable
to charged particle fluxes¾ 10x in Hadron Monitor¾ 10x in Muon Monitor 1• From Beam Dump

¾ Smaller in other locations• Neutrons create ionization bynuclear recoils• Measured ionization fromPuBe neutron sources¾ 1-10 MeV¾ 55 Ci

November 10, 2003

Robert Zwaska
NBI 2003

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Neutron Signals
D. Indurthy et al, submitted to Nucl. Instr. Meth.

He GasAr GasIon Pairs / cm

He GasAr GasNeutrons

1.1 ± 0.2

9.6 ± 2.6

Charged Particles

16120

November 10, 2003

Robert Zwaska
NBI 2003

Results ⇒signal:noise is 1:1in monitors?
-preliminary16System Design•

Hadron Monitor¾ 7x7 grid → 1x1 m2• 1 mm gap chambers¾ Radiation Hard design¾ Mass minimized for residual activation• 57 Rem/hr•

Muon Monitors¾ 9 tubes of 9 chambers each → 2.2x2.2 m2• 3 mm gap chambers¾ Tube design allows repair•

High Voltage (100-500 V) applied over He gas¾ Signal acquired with charge-integrating amplifiers

Radiation Damage Tests@ UT Nuclear Engineering Teaching Lab Reactor

Ceramiccircuit
board
Swagelok

PEEK

November 10, 2003

• Delivered 12GRad ≈ 9NuMIyrsAl2O3ceramic

Robert Zwaska
Kapton cable
NBI 2003

Ceramicputty

18

Hadron Monitor Construction

rear feedthrough basefront window
November 10, 2003

Robert Zwaska
NBI 2003

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Muon Monitor Construction• All detectors
completeNovember 10, 2003

Robert Zwaska
NBI 2003

D. Indurthy, M. Lang,S. Mendoza, L. Phelps, M. Proga,
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N. Rao, R. Zwaska

Assembly
Signal Cables

1 µCi 241Am αCalibration Source

Tray

HV cables
November 10, 2003

Robert Zwaska
NBI 2003

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Muon Monitor Calibration•Establish relative calibration of all 270chambers to <1%.
•Irradiate every chamber with 1Ci
Am241 source (30-60 keV γ’s)
S. Mendoza, D. Indurthy, Z. Pavlovich

26 / (27+5) Tubes
Calibrated•Precision of ion current ~0.1pA•Results show ~10% variations
due to construction variations
November 10, 2003

Robert Zwaska
NBI 2003

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Summary• Hadron & Muon Monitors provide information on:¾ Beam alignment (proton & secondary)¾ Target Integrity¾ Optics Quality• Signals come from hadrons, muons, and neutrons• Variable energy beam allows more information to be collected• Detector hardware tested at high intensity¾ Linearity is adequate¾ Behavior is understood through simulation• Neutron backgrounds estimated & characterized¾ Neutron signal might be comparable to (other) hadron signal• Systems designed, built, & calibrated¾ Components tested for radiation damage
November 10, 2003

Robert Zwaska
NBI 2003

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