Simulations of LBNF/DUNE Muon Monitors Jeremy Lopez University of - - PowerPoint PPT Presentation

Simulations of LBNF/DUNE Muon Monitors

Jeremy Lopez University of Colorado 23 January 2017

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Muon Monitoring Basics

• Muons + neutrinos produced in hadron decays
• Muon decays can produce more neutrinos
• Want to measure muons in alcove(s) downstream of absorber
• Typical rate of ~107-108 muons / cm2 / spill

– Need to handle large signals

• Almost no protons, but large neutron flux

– need detectors that will survive for long periods of time

Target Horns Decay Pipe Absorber ND Hall Station 1 More Alcoves/Stations Neutrino Muon Pion

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Muon Monitoring at NuMI

• This past year:
• Component failure caused upstream end
• f Horn 1 to be misaligned vertically by 3-

4 mm

• Was not discovered for quite some time
• Large enough to affect on-axis flux
• Can muon monitors find this? With

sufficient manpower and good enough precision, yes. NuMI systems not quite up to task

• J. Hylen

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NuMI Muon Monitor Data

• G. Brunetti

https://indico.fnal.gov/conferenceDisplay.py?confId=11797

MM1 signal decreases from October 2015 to mid-Jan. 2016, then is fairly flat MM3 signal increases from October 2015 to mid-Jan. 2016, then is fairly flat MM1 Total Signal MM3 Total Signal

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NuMI Muon Monitor Data

• G. Brunetti

https://indico.fnal.gov/co nferenceDisplay.py? confId=11797

Position [cm] Position [cm] Position [cm] Position [cm]

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Muon Monitors for LBNF/DUNE

• Have several detector stations where we can measure muons
• Several detector types to measure both the spatial distribution and

energy distribution of muons

pion muon neutrino Station 1: Ionization detector array, Cherenkov detector Shielding & additional stations: Ionization detectors, stopped muon counters, etc Hadron absorber ~3.7 m iron ~2 m iron Absorber hall & muon alcove (not to scale)

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Hadron Absorber Reference Design

• Several features that may affect muon measurements

– Spoiler + mask & sculpting: provide voids where muons can decay – Mask & sculpting: highly non-uniform absorber profile even near beam center – Core size: muons beyond ~60 cm from beam center travel through much more material

• These will (1) shape the signal, so the profile shape may tell us mostly about the absorber geometry, and (2)

bias the signals toward the nominal beam center, so that the measured centroid or peak is always at or near the same position

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Beam Simulations

• 109 POT per data set
• 90 GeV proton beam, 1.6 mm beam width
• Using NuMI-style target (rectangular fins, 10 mm

wide), 2 m long

– Few, if any, protons hit absorber

• 3-horn optimized beamline geometry (see BOTF

report)

• Exact numbers will change as beamline design is

refined & finalized

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Hadron Absorber in Simulation

• Reference design

– Engineered for reference beam – Reference beam: 15% of protons hit absorber – Optimized beam & long target: almost no

protons hit absorber

– May be able to simplify with optimized

beamline

• Simplified geometry:

– No spoiler – No mask – No sculpting of aluminum layers – Wider aluminum core (1.52 m square to 2.8 m) – Much more uniform, but need to see what can

be done given safety and cost constraints

Cartoon – Not to scale Cartoon – Not to scale Air Steel Aluminum

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What Do We Measure?

X Profile, |y|<7.5 cm X Profile, |y|<7.5 cm Reference Absorber Simplified Absorber All profiles in this talk: For ionization detector just downstream of absorber, perpendicular to beam Typically: Sample every 25 cm or so (~ every 5 points in these plots) Ionization Signal Ionization Signal

X [cm] X [cm] Y [cm] Y [cm]

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What Do We Measure?

• Exponential-like distribution
• f muon energies in alcoves
• Initial energies above 5 GeV
• Same hadrons give

neutrinos with E above 3 GeV

Muons just downstream of absorber Neutrinos associated with muons found in alcove with r<1 m from beam center Initial energies of muons found in alcove r < 20 cm

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Altered Beam Conditions Simulated

Change Type Amount Beam X 1 mm Beam Y 2 mm Beam Width 100 micron Horn Current 3 kA (1%) Target Density 5% Horn A X (shift) 1 mm Horn A Y (shift) 2 mm Horn A X (tilt) 2.5 mm Horn A Y (tilt) 2.5 mm Horn B X (shift) 2.5 mm Horn B Y (shift) 2.5 mm Horn B X (tilt) 2.5 mm Horn B Y (tilt) 2.5 mm Changes considered will generally generate deviations in ND total flux of 1-5% DocDB-1486 More details in muon monitor tech notes.

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Changes in the Neutrino Flux at Near Detector

Beam X Shift Target Density Reduction Horn A x Shift Horn A y Tilt

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Beam Shifted in X

• For reference absorber, still peaks at nominal beam center

–

Would need to look for a small asymmetry

• Simple absorber shows a much larger shift in the profile shape

Normal beam Beam Shifted by +1 mm Normal beam Beam Shifted by +1 mm Reference Absorber Simplified Absorber Ratio,

• Ref. Abs.

Ratio,

• Simp. Abs.

Altered Beam / Nominal Beam

• Ion. Det. Signal
• Ion. Det. Signal

Peak at 0 Peak clearly shifted Some asymmetry present Very clear asymmetry

Centroid: 0.04 cm

• Gaus. Mean: -0.47 cm

Centroid: -0.61 cm

• Gaus. Mean: -1.58 cm

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Horn A Shifted in Y

• Similar to beam shift: Hard to find changes in a fit, centroid,

peak, etc for the reference absorber, but an asymmetry still present

• Ion. Det. Signal
• Ion. Det. Signal

Normal beam Horn A Shifted by +2 mm Normal beam Horn A Shifted by +2 mm

• Ref. Abs.
• Ref. Abs.

Ratio

• Simp. Abs.
• Simp. Abs.

Ratio

Centroid: 2.61 cm

• Gaus. Mean: 3.16 cm

Centroid: 3.04 cm

• Gaus. Mean: 5.15 cm

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Target Density Reduction

• At E=90 GeV, the total

signal does not change much for the reference absorber

• No significant change in

shape

• Large increase in muon

flux at high energies

• Slight decrease at low

energies

Normal beam Target dens. reduced by 5%

Reference Absorber

Ratio = (fluence in altered beam)/(fluence in normal beam)

Muons just downstream of Absorber, r<20 cm

• Ion. Det. Signal

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More

• Measurements of the flux in a narrow energy band are

likely more useful than threshold measurements

• Ref. Abs.

Horn A y Shift

• Ref. Abs.

Horn A y Tilt (US end +2.5 mm in y, DS end -2.5 mm in y) Reduction in total flux Shape changes at max near 5 GeV

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Preliminary Requirements for Physics Monitoring

• To help identify beam problems, we'll want to

monitor:

– Mean position stability to ~1-2 cm precision – ~5 GeV muon flux stability to 2% precision – ~8 GeV muon flux stability to 4% precision – Total muon signal stability to 1-2% precision (within

2 m x 2 m square around nominal beam center)

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Conclusions (1)

• Reference absorber design suppresses

changes in the beam position

– Beam profile driven by absorber geometry not

beam physics

– Standard statistics such as centroid, peak position,

Gaussian fit mean, etc are not very meaningful

– Can still look for asymmetries but would be more

difficult and harder to interpret

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Conclusions (2)

• Muon spectrum measurements very important for measuring

beam problems

– Should measure the muon flux at least around 0, 5, and 8+ GeV – Measurements in narrow ranges with specialized spectrum-

sensitive detectors (stopped muon counters, Cherenkove detectors) also useful

– Exact amounts of shielding for an alcove would need some

• ptimization (have simulated flux just downstream of absorber, not

at different stations with different amounts of shielding)

• For 5 GeV, need ~3.7 m of iron shielding, 2 m more for 8 GeV
• Also possible that the reference absorber will create challenges for flux

measurements

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Backup

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Rui Chen NuMIX-doc 127

10% increase in flux In some energy bins between 2015 and 2016

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Ionization Detectors

• Create an array of detectors to

sample ionizing particles

• Measure the transverse beam profile
• Can extract information such as:

– Overall signal intensity – Peak position/signal centroid (i.e.

direction)

– Width – Timing (with solid state detectors)

• Monitoring: Look for changes (event

to event or long term trends) in signals

Example beam profile Place detectors at ~25 cm intervals Possible technologies: Ion chambers Solid state (diamond, silicon) Secondary emission detectors (for very high flux)

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Threshold Cherenkov Detectors

• Gas density determines Cherenkov threshold
• Fast signals, measures
• If left alone: Monitor flux for some particular subset of muon

kinematics

• Can also scan over gas density, detector angle to constrain the

muon spectrum at many different points with a single detector

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Stopped Muon Counter

• Stop low energy muons in a small detector

and measure Cherenkov light from Michel electrons

• Wait until after beam pulse ends to count

indivual decays

• Sample muon flux at different energies using

shielding or several alcoves

• Insensitive to many backgrounds (delta rays)
• Interpretation of signals more straightforward

than for Cherenkov detector, but more limited in what it could measure

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Horn A Shifted in X

• Similar to beam shift: Hard to find changes in a fit, centroid,

peak, etc for the reference absorber, but an asymmetry still present

• Ion. Det. Signal
• Ion. Det. Signal

Altered Beam / Nominal Beam Altered Beam / Nominal Beam

Normal beam Horn A Shifted by +1 mm Normal beam Horn A Shifted by +1 mm

• Ref. Abs.
• Ref. Abs.
• Simp. Abs.
• Simp. Abs.

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Horn Current Reduction

• Horn current reduced

by 3 kA (~1%)

• Shapes nearly identical
• Total signal reduced by

a bit more than 2%

Normal beam Horn I reduced by 1% Reference Absorber Total Signal: Charged particles within a 2.05 m x 2.05 m square around nominal beam center

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Horn A Y Shift

Reference Abs. Simplified Abs.

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Horn A X Tilt

• Very challenging to measure with profiles
• But, tilts with no shifts not very likely to develop

Reference Abs. Simplified Abs. Horn Beam X: +2.5 mm X: -2.5 mm

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Horn A Y Tilt

Reference Abs. Simplified Abs.

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Horn B X Shift

Reference Abs.

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Horn B Y Shift

Reference Abs. Simplified Abs. Horn B tilts and Horn C misalignments likely to be measurable in a realistic muon monitoring system

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Alcove Setup

• We will want at least 3 stations for detector systems:

– Just behind absorber – Stop 5 GeV muons (mu energy at alcove 1) – Stop ~8-10 GeV muons (mu energy at alcove 1)

• Multiple stations will provide flexibility & redundancy:

– allow for extra ionization counter stations, stopped muon counters, any

• thers

– Room for testing new detectors (useful in NuMI) – Have space in case monitoring needs change during LBNF running (high

energy mode, 2.4+ MW running, etc)

– Note: Current NuMI alcoves are large enough to accommodate all 3 types

• f detectors in a single alcove

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Muon System Requirements (Reference Absorber)

Beam Change Requirement to measure beam change X shift (1 mm) Mean x to 5 mm, x asymmetry to 1% or ~8 GeV flux to 4% Y shift (1 mm) Mean y to 2 cm, y asymmetry to 3% or ~5 GeV flux to 2% Horn Current (3 kA) Total signal to 2% or ~5 GeV flux to 2% Target Density (5%) ~8 GeV flux to 4% Horn A X shift (1 mm) Mean x to 1 cm, x asymmetry to 2%, or total flux to 1% Horn A Y shift (2 mm) Mean y to 3 cm, ~5 GeV flux to 4%, or total flux to 2% Horn A X tilt (2.5 mm) ~5 GeV flux to ~2% Horn A Y tilt (2.5 mm) ~5 GeV flux to ~2% Horn B X shift (2.5 mm) Mean x to ~7 mm Horn B Y shift (2.5 mm) Mean y to ~ 1 cm Horn B tilts of a few mm, beam width reduction likely too difficult to measure Also note, haven't looked at threshold-based measurements yet

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Muon System Requirements (Standard Absorber)

Beam Change Requirement to measure beam change X shift Mean x to 1.5 cm, x asymmetry to 2% or ~8 GeV flux to 4% Y shift Mean y to 4 cm or y asymmetry to 4% Horn Current Total signal to 2% Target Density ~8 GeV flux to ~4% Horn A X shift Mean x to 2 cm or total flux to 1% Horn A Y shift Mean y to 5 cm, ~5 GeV flux to 4%, or total flux to 2% Horn A X tilt ~5 GeV flux to ~2% Horn A Y tilt ~5 GeV flux to ~2% Horn B X shift Mean x to ~1 cm Horn B Y shift Mean y to ~2 cm Horn B tilts of a few mm, beam width reduction likely too difficult to measure