What UV laser can do in LAR TPC (and what it can't) I. Kreslo - - PowerPoint PPT Presentation

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What UV laser can do in LAR TPC (and what it can't)

• I. Kreslo

3.12.2015 DUNE CALIBRATION WG meeting

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Straight ionization tracks by UV pulsed laser

A Prototype liquid Argon Time Projection Chamber for the study of UV laser multi-photonic ionization

• B. Rossi (Bern U., LHEP) et al.. Jun 2009. 26 pp. JINST 4 (2009) P07011

Measurement of the two-photon absorption cross-section of liquid argon with a time projection chamber

• I. Badhrees (Bern U., LHEP) et al.. Dec 2010. 16 pp. New J.Phys. 12 (2010) 113024

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Effects contributing to the observable ionization

• 1. Beam divergence: nominal 0.5 mrad, can change at mirrors!)
• 2. Beam absorption: does not seem to be an issue...
• 3. Rayleigh scattering
• 4. Refraction on density gradients
• 5. Non-linear effects (Kerr-induced self-focusing)
• 6. Charge amplifier response function

“Attenuation of vacuum ultraviolet light in liquid argon” A. Neumeier et al, Eur. Phys. J. C (2012) : λatt> 100 m at 266 nm

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Index of refraction, Rayleigh scattering length, and Sellmeier coecients in solid and liquid argon and xenon Emily Grace, James Nikkel, http://arxiv.org/pdf/1502.04213v1.pdf

Rayleigh scattering at 266 nm (λR≈40m at 266 nm)

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Non-linear effects (Kerr-induced self-focusing)

For silica, n0 ≈ 1.453, n2 ≈ 2.4×10−20 m2/W,[12] and the critical power is Pcr ≈ 2.8 MW. @10 mJ per 5 ns pulse we are at P=2 MW ! To be calculated for LAR !!

AC Kerr effect: Self-focusing at beam power P > Pcr Is it self-focusing? Not 100% sure...

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2009 JINST 4 P07011 NJP 12 (2010) 113024

Pulsed laser, t ~ 5 ns Frep from 0 to 10 Hz 266 nm, ~10 mJ/pulse Straight ionisation tracks by UV pulsed laser Charge attenuation → LAr purity Track curvature → Drift field Track divergence → Tr. diffusion End peak → Lon. diffusion Charge density → dE/dX

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dE/dX calibration based on charge density Multi-photon absorption:

Measurement of the two-photon absorption cross- section of liquid argon with a time projection chamber

• I. Badhrees (Bern U., LHEP) et al.. Dec 2010. 16 pp.

New J.Phys. 12 (2010) 113024

N e N0t =σ F

n

t=5ns,σ=1.2 ˙ 10

−56 cm 4/s ,n=2

λ=266nm→4.67eV =7.510

−19J

@1mJ /5 ns pulse,@beam 5 x5 mm

2

F≈10

24 ph

cm

2s

; Ne N0 =510

−17e/ atom

N0/dx=5.310

21 atoms/cm ;dN e/dx=2.610 5e/cm

for MIP: dN e/dx≈910

4e/cm

Systematic errors:

• 1. Charge life time (purity)
• 2. Beam divergence (0.5 mrad)
• 3. Rayleigh scattering
• 4. Preamp response
• 5. Refraction on gradients
• 6. Non-linear (self-focusing)

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• I. Kreslo for DUNE CALIBRATION WG meeting

03/12/15

Charge attenuation measurement (ARGONTUBE data) Charge life time (purity) evolution

Charge vs drift time LASER track Charge vs drift time muons

Purification Systematic errors:

• 1. Beam divergence (0.5 mrad)
• 2. Rayleigh scattering
• 3. Refraction on gradients
• 4. Non-linear (self-focusing)

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• I. Kreslo for DUNE CALIBRATION WG meeting

03/12/15

ARGONTUBE geometry/field calibration with laser Laser track Muon track Before correction After correction Systematic errors:

• 1. V(E,T) dependence
• 2. Refraction on gradients
• 3. Non-linear (self-focusing) – so far didn't observe track deviation at charge blobs

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Expected improvement in coordinate accuracy (uBooNE example) 9 cm → O(mm)

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• I. Kreslo for DUNE CALIBRATION WG meeting

03/12/15

MicroBooNE geometry/field calibration with laser

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• I. Kreslo for DUNE CALIBRATION WG meeting

03/12/15

Transverse diffusion (ARGONTUBE data) Laser ionisation track Systematic errors:

• 1. Charge life time (purity)
• 2. Beam divergence (0.5 mrad)
• 3. Rayleigh scattering
• 4. Refraction on gradients
• 5. Non-linear (self-focusing)

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• I. Kreslo for DUNE CALIBRATION WG meeting

03/12/15

LASER-induced track Track end: Photoelectrons from cathode Cloud of photoelectrons Longitudinal diffusion (ARGONTUBE data)

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• I. Kreslo for DUNE CALIBRATION WG meeting

03/12/15

PRELIMINARY

DL=3.8 ± 0.1 (stat.) +1.7 -0.9 (sys.) cm2/s Longitudinal diffusion (ARGONTUBE data) Systematic errors:

• 1. Amplifier response
• 2. Drift field uncertainty

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Summary matrix for 40 m long beam

dE/dx

Electron τ

E drift Dt Dl

Beam divergence

XXX X X

Beam absorption

X X X

Rayleigh scattering

X X X (at>10m) X

Refraction on density gradient

X X

Non-linear effects (Kerr- induced self- focusing)

X X XXX

Preamp response

XXX X

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UV laser calibration system

Conceptual design

Goal: to provide straight ionisation tracks for field/purity calibration Tool: 4 UV lasers, each with steerable mirror feed-through

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Primary Source: Nd:YAG laser (Surelite I-10) from Continuum, Inc. with frequency multiplication: Output beam 266 nm , 60 mJ, 5 ns. Maximum repetition rate 10 Hz. Beam divergence 0.5 mrad Beam diameter about 5 mm

UV laser calibration system

Primary beam generator

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UV laser calibration system

Rotating flange and steerable mirror

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UV laser calibration system

Cryostat and detector orientation

Beam Four steerable-mirror poles lowered from the cheminee top flange

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UV laser calibration system

Cryostat and detector orientation

Beam

Laser beams

Steerable

• ptical FT

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UV laser calibration system

Entering TPC field cage

Steerable mirrors

Laser beams