Radiation damage and recovery Radiation damage and recovery of PWO - - PowerPoint PPT Presentation

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Radiation damage and recovery Radiation damage and recovery of PWO - - PowerPoint PPT Presentation

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Radiation damage and recovery Radiation damage and recovery of PWO crystals of PWO crystals R.W.Novotny PANDA-EMC GSI 2010 0222 1 quantitative studies 1 1 1 1 1 light intensity = 6.110 16 ph/s 1 LED, I= 0.54*10 17 ph/s light

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R.W.Novotny PANDA-EMC GSI 2010 0222 1

Radiation damage and recovery

  • f PWO crystals

Radiation damage and recovery

  • f PWO crystals
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R.W.Novotny PANDA-EMC GSI 2010 0222 2

wavelength / nm

dk / m-1 blue light (464 nm)

light intensity=5.8*1016 ph/s

0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 300 400 500 600 700 800 900

1 min. after irr. 31 min. after irr. 2 min blue light illum. 180 min blue light illum.

Time of 90% recovery: 9000 min. @spontaneous; 23 min. @ 464 nm

quantitative studies

0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 300 400 500 600 700 800 900

1 min. after irr. 31 min. after irr. 10 min infrared light illum. 160 min infrared light illum.

IR light (940 nm)

light intensity=2.4·1017 ph/s Time of 90% recovery: 370 min.@940nm

0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 300 400 500 600 700 800 900

1 min. after irr. 31 min. after irr. 10 min. light illum. 340 min. light illum.

IR light 1060 nm

light intensity = 6.1·1016ph/s Time of 90% recovery: 1150 min.@1060 nm

0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 20 40 60 80 100 120 140 160 180 200

1 LED, I= 0.54*1017 ph/s Α1= 0.25 τ1= 24 min. Α2=0.54 τ2= 260 min. 4 LED, I= 2.4*1017 ph/s Α1=0.37 τ1= 16 min. Α2=0.43 τ2= 220 min. 2 LED, I= 1.2*1017 ph/s Α1=0.31 τ1= 20 min. Α2=0.46 τ2= 244 min.

time of illumination / min

dk @ 420nm / m-1 IR light (940 nm)

0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 50 100 150 200 250 300 350 400

4 LED, I= 6.1*1016 ph/s Α1=0.41 τ1= 55 min. Α2=0.36 τ2= 748 min.

IR light 1060nm

4 LED, I= 6.1*1016 ph/s Α1=0.41 τ1= 55 min. Α2=0.36 τ2= 748 min.

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R.W.Novotny PANDA-EMC GSI 2010 0222 3

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R.W.Novotny PANDA-EMC GSI 2010 0222 4

implications for final EMC operation

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R.W.Novotny PANDA-EMC GSI 2010 0222 5

stimulated recovery of PWO @ T=-25oC

photomultiplier

PWO-II crystal γ-source LEDs

  • measurement at T=-25oC
  • irradiation with 30Gy (60Co)
  • damage and recovery characterized by light yield (60Co)
  • illumination with LEDs of different color
  • crystals of different radiation hardness (dk)
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R.W.Novotny PANDA-EMC GSI 2010 0222 6

stimulated recovery of PWO @ T=-25oC

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R.W.Novotny PANDA-EMC GSI 2010 0222 7

understanding of the mechanism

recovery is a thermodynamical process which can be accelerated by:

  • significant heating
  • photons:
  • ptical bleaching (ionization of color centers)

stimulated recovery (intra-center resonant transition) initiated by minimum photon energy (IR)

∑

− − =

j j j i T i

t ) I b w exp( n n ) kT / E exp( A w

TA i i T

− =

with

necessary conditions:

  • at least one energy level above the radiating state
  • re-trapping should be strongly suppressed (small number of centers)
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R.W.Novotny PANDA-EMC GSI 2010 0222 8

1 ionization of FTDo, 2 radiative/non-radiative recombination, 3 intra-center absorption in FTDo, 4 non-radiative relaxation, 5 radiative/non-radiative recombination of FTDo.

ionization and stimulation processes in PWO

IR photons

photons: UV to visible

CB

VB 2

1 3 4 5

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R.W.Novotny PANDA-EMC GSI 2010 0222 9

total fluence of 24 GeV/c protons: (9.87 ± 0.69)·1012 p/cm2

first attempt of recovery of damage due to protons

in collaboration with F. Nessi-Tedaldi et al.

360nm 420nm 620nm

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R.W.Novotny PANDA-EMC GSI 2010 0222 10

stimulation with blue light (464nm)

τshort= 400 min. (6h. 40min.) τlong= 44460 min. (741 h.)

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R.W.Novotny PANDA-EMC GSI 2010 0222 11

irradiation with 30Gy (60Co) and subsequent recovery with blue light

before repeated γ-irradiation stimulation with 464 nm spontaneous recovery

τshort= < 1 min. τlong = 30 min.

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R.W.Novotny PANDA-EMC GSI 2010 0222 12

irradiation with 30Gy (60Co) and subsequent recovery

464 nm illumination: τ1 <1 min. τ2 =20-40 min. start of illumination before γ-irradiation start of illumination before γ-irradiation 949 nm illumination: τ1 = 1 h τ2 = 28h

all data are normalized to the measurement before irradiation at CERN

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R.W.Novotny PANDA-EMC GSI 2010 0222 13

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R.W.Novotny PANDA-EMC GSI 2010 0222 14

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R.W.Novotny PANDA-EMC GSI 2010 0222 15

  • ngoing studies
  • 1. EPR studies of

1. PWO-II and PWO-I crystals before irradiation 2. Studies of irradiation with photons or protons 3. Impact of stimulated recovery

  • 2. Direct measurement of optical transmission of cooled crystals

1. Before/after irradiation 2. Measurement of recovery times 3. Impact of stimulated recovery

  • 3. Determination of optimum wavelength and photon flux
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R.W.Novotny PANDA-EMC GSI 2010 0222 16

up to 5 γ-sources

60Co (~1.25MeV)

Bq 10 7 . 2 dt dN

13

⋅ =

radiation center @ Giessen

photo- spectrometer irradiation and recovery

  • f cooled crystals

integral dose: 15.5Gy

T = -10oC

emission

  • f PWO
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R.W.Novotny PANDA-EMC GSI 2010 0222 17

radiation induced absorption Δk (MoO4)3-