Update on Simulation Studies of the CEDAR Optics

Helen Heath9th December 2009

Reminder (see N.Brook’s talk from August)

• Use Lau’s CEDAR simulation• provide Cerenkov photons to current quartz

window • -> position(x,y,z) and direction(nx,ny,nz) and

wavelength• Optical path simulation

• Use ROOT and its geometry manager

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Z=646mm

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Z=996mm

Parabaloidal “cones”10mm depth 25mm depth

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Summary of results in August

• 10mm cone • 82-87% photon reach PMT cathode• 68-90% of photons reflected off cone reflect

off PMT window• 25mm cone

• 87-91% photon reach PMT cathode• 29-67% of photons reflected off cone reflect

off PMT window

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Cone v Parabaloid

80.0%

82.0%

84.0%

86.0%

88.0%

90.0%

92.0%

94.0%

600 700 800 900 1000

25mm Conical collectors

25mm Parabaloid Collectors

10mm Short ConicalCollectors10mm Parabaloid Collectors

Efficiency for photons to reach the PMT cathode v z position

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Efficiency for different cone depths

80.0%

82.0%

84.0%

86.0%

88.0%

90.0%

92.0%

500 700 900 1100

10mm cone15mm cone20mm cone25mm cone30mm cone12mm cone11mm cone9mm cone

Shown for conical collection cones

Note: there is little increase in efficiency one the cones are above 15mm in length

The parabaloid is similar but the efficiency falls more quickly

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Source of Losses

• Previous simulations assumed losses at surfaces due to • 5nm roughness for mirror• 10nm roughness for cones

• Look at cone roughness

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10nm Roughness

-5.0%

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

0 5 10 15 20 25 30

Reflection at the mirrorRoughness of coneReflection from PMTescapedtotal loss

Photon loss v cone depth z=646

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Escapees10

5nm Roughness

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

0 5 10 15 20 25 30

Reflection at the mirrorRoughness of coneReflection from PMTescapedtotal loss

Photon loss v cone depth z=64611

15nm Roughness

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

0 5 10 15 20 25 30

Reflection at the mirrorRoughness of coneReflection from PMTescapedtotal loss

Photon loss v cone depth z=646

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Summary of Efficiency Studies

• Dominant contributions to the photon loss are• Photons escaping the system for depth<7mm• Reflection from the PMT surface

7mm<depth<~10mm• Beyond 10mm the loss at the cone surface

may become the dominant contribution but it increases slowly above ~15mm

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Photon distributions at PMT

• Nick’s studies observed a double peak in the photon angle at the PMT.

• Confirmed to be photons reflected from the cone and those that enter directly (see next slide)

• Also noted that the distribution across the PMT face is different for these two cases

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10mm cone, photon angle to PMT face. Red photons not reflected from cone, blue photons reflected from cone

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25mm cone, photon angle to PMT face. Red photons not reflected from cone, blue photons reflected from cone

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1725mm cone, photon position at PMT face. Red, photons not reflected from cone, black photons reflected from cone

Efficiencies for photons from Pions

• 25000 photons• 25mm cone

• Efficiency 0.10% for all z

Z 646 696 746 796 846 896 946 996# Arrived at PMT 25 26 25 26 23 26 25 24

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Future plans

• To look at the muon halo • Feed in any mechanical design constraints

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