We investigated the darkening of two high OH- content quartz fibres irradiated with 24 GeV protons at the Cern PS facility IRRAD. The two tested fibres have a 0.6 mm quartz core diameter, one with hard plastic cladding (qp) and the other with quartz cladding (qq). These fibres were exposed at about 1.25 Gigarad in 3 weeks. The fibres became opaque below 380nm, and in the range 580-650 nm. The darkening under irradiation and damage recovery after irradiation as a function of dose and time are similar to what we observed with electrons. The typical attenuation at 455 nm are 1.44 + - 0.22 and 2.20 + - 0.15 dB/m at 100 Mrad for qp and qq fibres, respectively. The maximum damage recovery is also observed near this wavelength

Bakirci, N M

Cankocak, Kerem

Cerci, Salim

Gülmez, Erhan

Merlo, Jean-Pierre

Onel, Yasar

Ozok, Ferhat

Schmidt, Ianos

Sonmez, Nasuf

Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment

CERN Document Server

Available on CMS information server CMS NOTE CMS NOTE 2007/003The Compact Muon Solenoid ExperimentMailing address: CMS CERN, CH-1211 GENEVA 23, SwitzerlandCMS Note5 JAN 2007Radiation-hardness measurements of high OH−content quartz fibres irradiated with 24 GeVprotons up to 1.25 Grad.K. Cankoc‚aka), N. M. Bakrcb), S. C‚ erc‚ib), E. G¤ulmezc), J.P. Merlod), Y. Oneld), F. ¤Ozoke), I. Schmidtd), N.S¤onmezf)a) Mugla University, Department of Physics, Mugla, Turkeyb) Cukurova University , Department of Physics, Adana, Turkeyc) Bogazici University, Department of Physics, Istanbul, Turkeyd) University of Iowa, Department of Physics and Astronomy, Iowa City, USAe) Istanbul University, Department of Physics, Istanbul, Turkeyf) Ege University, Department of Physics, Izmir, TurkeyAbstractWe investigated the darkening of two high OH− content quartz bres irradiated with 24 GeV protonsat the Cern PS facility IRRAD. The two tested bres have a 0.6 mm quartz core diameter, one withhard plastic cladding (qp) and the other with quartz cladding (qq). These bres were exposed at about1.25 Gigarad in 3 weeks. The bres became opaque below 380 nm, and in the range 580-650 nm. Thedarkening under irradiation and damage recovery after irradiation as a function of dose and time aresimilar to what we observed with electrons. The typical attenuation at 455 nm are 1.44 ± 0.22 and2.20 ± 0.15 dB/m at 100 Mrad for qp and qq bres, respectively. The maximum damage recovery isalso observed near this wavelength.1 IntroductionFor a few years, in association with Turkish Particle Physics groups, the University of Iowa group investigated theradiation hardness of different types of bres for the Hadronic Forward calorimeter (HF) of the Compact MuonSolenoid experiment (CMS) at LHC. The results of darkening measurements of quartz bres of 0.3 and 0.4 mmcore diameter, irradiated with 500 MeV electrons up to 50 Mrad have already been published [1].To complete our knowledge of radiation damage in quartz bres and to investigate their possible use at the SuperLHC (SLHC) we initiated a high level irradiation with 24 GeV protons at CERN. About 1016protons/cm2 weresent onto 1.20 m of quartz bres, corresponding to a dose of 1.25 Grad (i.e. about 12 years of HF operation atLHC in the hottest tower).The bre radiation damage induced by protons exhibits the same well known behaviour as with electrons: highlight attenuation below 380 nm and in the band 550-680 nm. Moderate attenuation in the band 400-520 nm andpractically no attenuation above 700 nm was observed. The damage varies exponentially with dose; fast in the rsthours and slow after. Above 0.6 Grad we observe a new phenomenon: the radiation damage is not recoverablein the range 580-650 nm and below 380 nm. The two bres tested, 0.6 mm quartz core diameter, one with hardplastic cladding (qp) and the other with quartz cladding (qq), are supplied by the US rm Polymicro Tech. Inc.(PT).2 Experimental set-up and data acquisition2.1 Experimental set-upThe bres were installed, with their light support, on a remote controlled table (Fig. 1) at the CERN facility IRRAD[2].Figure 1: Experimental set-upThree loops of qq and qp bers (40 cm long) are wrapped together and placed with a slope of 2.5% relative to thebeam. The total irradiated length (L) is about 1.2 m. No material was inserted in front of the bres as in the caseof electrons [1].The 24 GeV proton beam at IRRAD was delivered as 3-4 sub-cycles in a (19.6± 3.0)s long supercycle [2]. Thisbeam delivers 1011p/cm2/burst in a spot of 2x2 cm2. The subcycle sharing changed during the irradiation. Thenumber of protons delivered was recorded and the dose calibration was done using thin Al samples. We regularlychecked the proton beam stability in position, width and time.The optical setup uses Ocean Optics components. The two-channel spectrometer (SD 2000) is the same as inelectron measurements [1]. At the beginning of irradiation we used a triggerable deuterium halogen lamp (d+h)and at the end a Xe lamp. These lamps deliver a wider spectrum than the range of the spectrometer (350-850 nm).The attenuation measurements were performed in-situ, the irradiated bres linked to the spectrometer and sourcewith 25 m long bers. The light was injected into a Y bre splitter and then into the qq and qp bres.2.2 Data acquisitionThe intensity of the light source (d+h) was quite low for the SD2000 that required an integration time of 1 sinducing a noticeable background (Fig. 2). In the range of 350-750 nm and with a dose of about one Grad, the2signal strength in the SD2000 was still signicant. The qp channel was less sensitive than the qq one. The rate oflight ashes and data acquisition changed from one per cycle (19.6s) at the beginning of irradiation to one per 40cyc. (13min) and one per 80cyc. (26min) at the end according to the damage versus dose or time (see section 3).(1) (2)(4)(3)λ (nm) λ (nm)λ (nm)λ (nm)  c(λ)←ADC countsADC countsFigure 2: Evolution of the transmitted light spectra from a 1.25 m of qq bre as a function of dose (0 to 1.25 Grad).2.3 Dose estimateIn the 2.5% tilted bres, protons crossed 2.4 cm of quartz, well before the hadronic shower maximum, and one canonly consider the minimum energy loss by protons. Then the dose D(MeV/g) depends simply on the minimumenergy loss in quartz dE/dx = 1.70 MeV/(g/cm2) and the total number of protons/cm2 N.D(MeV/g) = N(dE/dx) (1)For 1016 protons/cm2, D = 1.70 1016MeV/g = 272 Mrad. At IRRAD with 4.6 1016protons/cm2, the totaldose of the proton irradiation is 1.25 Grad. The electron irradiations at LIL were done up to 50 Mrad [1].33 Analysis and resultsTo measure the attenuation in the bre samples we had to take data outside the spills of protons not to include theCherenkov light generated by protons. But the PS cycling structure was changing during the run and some runsincluded Cherenkov light, these runs were discarded. Then, the data are histogrammed in 10 nm wavelength binscentered at λi . Runs are arranged in groups covering a few minutes of irradiation at the beginning and hours after100 Mrad dose.3.1 Analysis methodWe rst checked that in absence of input light the spectrometer background is independent of λ, dose and time.We added all the background distributions corresponding to each λ bin to get an overall background distribution(Fig.3), which we t with a Moyal distribution. The position b of the maximum in ADC counts is taken asbackground in each λ bin, for a given lamp and spectrometer channel at a certain dose and time.At a given dose D in the bin λithe raw signal distribution S(λi, D) in ADC counts starts at the cusp value c(λi, D)(Fig.4) and exhibits a Landau shape due to the background entanglement. The distributions above c(λi, D), i.e.[S − c](λi, D), are similar for each i bin and characterizes the background entanglement. Summing over the λibins one gets the total distribution in ADC countsST (D) =∑i[S − c](λi, D) (2)Fitting ST (D) with a Moyal (Landau) function, gives the maximum (µ(D)) of the ST (D) distribution (Fig.4). Weassume that the signal transmission intensity (I(λi, D)) can be expressed as a function of c, µ and b asI(λi, D) = c(λi, D) + µ(D) − b (3)3.2 ResultsWe calculate the ratios I(λ, D)/I(λ, 0) which decrease as a function of dose as shown in Figs. 5 to 8 giving thetypical behaviour at 455 and 615 nm for qq and qp bres. The transmitted light attenuation in the bre is wellrepresented by the following function [3].A(λ, D) = α(λ)[D/Ds]β(λ) (4)α and β parameters for qq and qp bres are determined by tting the ratios as a function of wavelength and dose.I(λ, D)/I(λ, 0) = exp[−(L/4.343)α(λ)(D/Ds)β(λ)] = exp[−A(λ, D)L/4.343] (5)Choosing a scale factor Ds = 100 Mrad, and L being expressed in meters, α is the attenuation at 100 Mrad, indB/m . The results for qq and qp bres are shown in (Figs. 9 and 10) for all wavelengths and in Table 1 for455 and 615 nm. For the qp bre the results are the mean of two successive 10 nm bins to increase the statistics.Statistical errors are larger than those in electron irradiations because of the lower light intensity and some beamunstability. Comparing to the former analysis of electron irradiation data we xed the systematic errors to be∆α= 0.15 independent of lambda and ∆ββ = 0.05 in the range 455−600 nm and 0.10 below 400 nm or above600 nm.Table 1: Values of α, β parameters at 455 and 615 nm for qq and qp bres of 0. 6 and 0.3 mm core diameterirradiated with protons.Fibre α(455− 460 nm) β(455− 460 nm) α(615− 620 nm) β(615− 620 nm)qq (0.6) p 2.20± 0.06 0.53± 0.013 6.37 ± 0.15 0.66± 0.01qp (0.6) p 1.44± 0.16 0.44±0.05 6.51 ± 0.26 0.45± 0.02qp (0.3) e− 1.54± 0.02 0.33±0.001 6.13 ± 0.06 0.60± 0.014The values of α and β parameters for qq and qp bres irradiated with protons are in good agreement with theresults for 0.3-0.4 mm core diameter irradiated with electrons, as long as they are drawn by Polymicro Techn. withthe same type of quartz. The ts up to 1.25 Grad near 450 nm show that the qq bre has an higher attenuation thanqp bre. The t of proton data up to 50 Mrad like the electron data [1] this difference disappears.01002003004005000 500 1000 1500 2000 2500 3000 3500Background distribution (qq) ADC values0250500750100012501500175020000 500 1000 1500 2000 2500 3000 3500Overall signal distribution (qq)ADC valuesFigure 3: Overall background distribution in ADCcounts and the Moyal function t dening the back-ground b as the position of the maximum for qq -bre.Figure 4: Overall background distribution ST (D) andthe Moyal function t dening the additional value”µ(D)” as position of the maximum for qq bre.4 Radiation damage recovery4.1 Fit the recovery dataThe radiation damage recovery was measured in qq and qp bres after a dose accumulation of 0.4 Grad (204 hoursof irradiation). The qq bre recovery was also measured after 1.25 Grad (605 hours). The qp ber broke beforethe end of maximum irradiation. We are not sure of the cause of the breakage. Nevertheless the steep decreaseof the transmitted light in qp bre above 1 Grad (Fig.7) favors the hypothesis of cladding deterioration. The timeevolution of defects in quartz can be described by exponential functions or by their approximate form at low valuesof the exponent.Q(λ, t) = Q(λ, 0) exp[−( tτ(λ))η](6)For small damage recovery effect, τ(λ) gets large values and it is impossible to t the data. For this reason we useΓ(λ) as second parameterΓ(λ) =( 1τ(λ))η(λ)(7)We choose to t the recovery data, attenuation versus time, with the following function (as was done in ref. [1] and[3])AD(λ, t) = A(λ, D)/(1 + [γ(λ)( ttirr)η(λ)]) (8)500.20.40.60.810 2 4 6 8 10 12I(D) / I(0) at λ= 455 nmqq fibreD/Ds00.20.40.60.810 2 4 6 8 10 12I(D) / I(0) at λ= 615 nmqq fibreD/DsFigure 5: I(D)/I(0) for qq bre versus dose at 455 nm. Figure 6: I(D)/I(0) for qq bre versus dose at 615 nm.00.20.40.60.810 2 4 6 8 10 12I(D) / I(0) at λ= 455 nmqp fibreD/Ds00.20.40.60.810 2 4 6 8 10 12I(D) / I(0) at λ= 615 nmqp fibreD/DsFigure 7: I(D)/I(0) for qp bre versus dose at 455 nm.The t is done up to 1 Grad.Figure 8: I(D)/I(0) for qp bre versus dose at 615 nm.6012345678910350 400 450 500 550 600 650 700 α (dB/m)λ (nm)0.20.30.40.50.60.70.8350 400 450 500 550 600 650 700 βλ (nm)Figure 9: α parameters versus λ for qq and qp bres,corresponding to the t of irradiation data up to 1.25Grad.Figure 10: β parameters versus λ for qq and qp bres,corresponding to the t of irradiation data up to 1.25Grad.Where AD(λ, t) is the value of the light attenuation at the post exposure time t (in hour) after an irradiation at adose of D in a time tirr . The parameter γ(λ) being related to τ(λ) as,τ(λ) = tirr/(γ(λ))1/η(λ) (9)Figures 11-12 show the decrease of the attenuation versus time, expressing the radiation damage recovery for qqand qp bres at 455-460 nm after 400 Mrad irradiation. Figures 13-14 show the corresponding increase of thetransmitted signal.Fitting the recovery data with function (8) one gets the parameters γ and η versus λ shown in Figures 15-16 forthe qq and qp bres. In Table 2 the γ and η values at 455 nm and 615 nm for proton irradiation are presented andcompared with the electron irradiation results [1]. The τ values are recalculated according to Eq. (9).One notices a strong recovery maximum near 450 nm with γ values close to 1 and a steep decrease below 400 nmand above 500 nm. The qq data exhibits the shrinkage of the peak between 400 Mrad and 1.25 Grad correspondingto the absence of recovery below 380 nm and above 600 nm. The quartz becomes opaque to these wavelengths athigh dose.Table 2: Values of γ and η parameters at 455 and 615 nm for qq and qp bres of 0. 6 mm core diameter (protonirradiation) and 0.3 mm core diameter (e− irradiation at LIL). At 455 nm the recovery lifetime τ is calculatedaccording Eq.(9), at 615 nm τ is meaningless regarding the errors.Fibre γ(455) η(455) τ(455) in h γ(615) η(615)qq (204 h) 0.93± 0.25 0.30± 0.08 208 ± 57 0.18± 0.11 0.25± 0.17qq (605 h) 0.79± 0.01 0.22± 0.01 635 ± 13 0.03± 0.01 0.57± 0.45qp (204 h) 0.89± 0.18 0.30± 0.06 213 ± 47 0.18± 0.20 0.49± 0.33qp (e− 45 h) 1.60± 0.02 0.26± 0.01 40 ± 3 0.077± 0.004 0.19± 0.0570.60.650.70.750.80.850.90.9511.051.10 1 2 3 4 5 6 7 8AD(t)/A(D) versus time (hour) for qq , λ=  455  nm0.60.650.70.750.80.850.90.9511.051.10 1 2 3 4 5 6 7 8AD(t)/A(D) versus time (hour) for qp , λ=  455  nmFigure 11: Decrease of the bre light attenuation ver-sus the post irradiation time for the qq bre at 455-460nm after 400 Mrad irradiation.Figure 12: Decrease of the bre light attenuation ver-sus the post irradiation time for the qp bre at 455-460nm after 400 Mrad irradiation.0.911.11.21.31.41.50 1 2 3 4 5 6 7 8I(t)/I(0) versus time (hour) for qq , λ=  455  nm0.90.9511.051.11.151.21.250 1 2 3 4 5 6 7 8I(t)/I(0) versus time (hour) for qp , λ=  455  nmFigure 13: Increase of the transmitted signal versusthe post irradiation time for qq bre at 455-460 nmafter 400 Mrad irradiation.Figure 14: Increase of the transmitted signal versusthe post irradiation time for qp bre at 455-460 nmafter 400 Mrad irradiation.800.20.40.60.811.21.4350 400 450 500 550 600 γλ00.10.20.30.40.50.6350 400 450 500 550 600 ηλFigure 15: Recovery parameters γ versus λ for qq andqp bres versus wavelength, after 205 hours and 605hours of irradiation.Figure 16: Recovery parameters η versus λ for qq andqp bres versus wavelength, after 205 hours and 605hours of irradiation.4.2 The damage recovery at 450 nmIn an iron-bre calorimeter like CMS-HF the Cerenkov light is detected by PMTs sensitive in the 400-500 nmrange. Near 450 nm the damage recovery is maximum and gamma is close to 1The knowledge of the evolution of light transmission in bres after a break in data taking is important for thecalibration measurements [4]. From Equations 3-8 one can easily derive the increase of transmitted signal ID(t)after an irradiation to a total dose D in time tirr.ID(t)/I(D) = exp[A(D)(L/4.343))(γtη/(tηirr + γtη))] (10)As an example we present in the Table 3 the values of the ratios ID(t)/I(D) for three post irradiation times t for a2 m long bre irradiated at 100 Mrad in tirr= 4800 hours with γ= 0.9, η = 0.25 and A = 1.6 dB/m.Table 3: Values of ID(λ, t)/I(λ, D) for three post irradiation times after the irradiation of 2 m of bre at 100 Mradin tirr= 4800 h, at 455 nm.t(h) 2.4 24 240 2400ID(t)/I(D) 1.06 1.12 1.22 1.37One can see from Table 3 what kind of correction might be applied to a calibration performed at a post data takingtime t to get the real calibration at the data taking time.The difculty to determine accurately the damage recovery parameters leads us to propose to monitor in situ thelight transmission in the quartz bre of the CMS-HF calorimeter during and after data taking.5 SummaryRadiation damage due to protons and damage recovery are in agreement within errors with our previous results ofelectron irradiations with the same type of quartz used by Polymicro Technology Inc.. The two types of irradiationwere quite different:- 24 GeV protons compared to 0.5 GeV electrons, in different geometries9- 1.25 Grad with protons compared to 50 Mrad with electrons- Different set-up and different bre sizesAs in electron irradiations we did not observe signicant differences in proton irradiation between qq and qp breup to 1 Grad. Near 450 nm the observed difference appears in the ts at high dose and above 1 Grad there is asteep decrease of the transmitted signal in qp bre (Figure 7).For doses above 0.5 Grad there is no recovery of damage below 380 nm and in the range of 580-650 nm, the quartzbecomes opaque.The PMTs detecting Cherenkov light are sensitive to the blue light (about 450 nm) emitted from the bres wherethe effects are maximum.For a 2 m qp bre with the parameters listed in Tables 1 and 2, one expects:-a decrease of 30% in light transmission resulting from a dose accumulation of 20 Mrad-an increase in light transmission by 22% ten days after an irradiation to 100 Mrad in 200 days.With a quartz-iron calorimeter like CMS-HF, the calibration [4] is done after the data taking. Also one shouldknow the change of response of HF bres between the end of data taking and the time when the calibration takesplace.As mentioned in ref. [5] at 470 nm there is a luminescence band with a rather long and not well measured lifetimeof 2-10 ms in quartz. This could explain the quartz radiation effects near 450 nm: relatively low darkening underirradiation and almost full recovery of the irradiation damage. But this quartz luminescence band is still not verywell known and merits to be investigated more seriously to improve our knowledge of the quartz material and tounderstand the consequences in a quartz-metal detector as the HF-CMS calorimeter.AcknowledgmentsWe thank Maurice Glaser responsible of the IRRAD facility who helped us in the installation of our set-up andcalibrated the dose received, the PS operators and technicians providing the proton beam, the SPS-PS coordinatorand the CMS test beam coordinator. We thank I.Dumanoglu for helpful discussions. We would also like to thankthe University of Iowa for their continuing support for this research. This work was supported by the US Depart. ofEnergy (DE-FG02-91ER 40664) and NSF (NSF-INT-98-20258) and the Scientic and Technical Research Councilof Turkey, TUBITAK, Turkish Atomic Energy Board (TAEK) and Bogazici University Research Fund (Grant no:06B302).References[1] I.Dumanoglu et al., Nucl. Inst. and Meth. in Phys. Res. A490 (2002) 444-455.[2] M. Glaser et al., Nucl. Inst. and Meth. in Phys. Res. A426 (1999) 72-77.[3] D.L. Griscom et al., Phys. Rev. Lett. 71 (1993) 1019.[4] CMS-HF collaboration, CMS NOTE 2006/044[5] L. Skuja, Journ. Non-Cryst. Solids 239 (1998) 16.10

Radiation-Hardness Measurements of High $OH^{-}$ Content Quartz Fibres Irradiated with 24 GeV Protons up to 1.25 Grad

We investigated the darkening of two high OH- content quartz fibres irradiated with 24 GeV protons at the Cern PS facility IRRAD. The two tested fibres have a 0.6 mm quartz core diameter, one with hard plastic cladding (qp) and the other with quartz cladding (qq). These fibres were exposed at about 1.25 Grad in 3 weeks. The fibres became opaque below 380 nm and in the range 580-650 nm. The darkening under irradiation and damage recovery after irradiation as a function of dose and time are similar to what we observed with electrons. The typical attenuation at 455 nm are 1.44 ± 0.22 and 2.20 ± 0.15 dB / m at 100 Mrad for qp and qq fibres, respectively. The maximum damage recovery is also observed near this wavelength. © 2007 Elsevier B.V. All rights reserved

Cankoçak, Kerem

Bakirci, M.N.

ÇERÇİ, Salim

Gülmez, E.

Merlo, J.P.

Onel, Y.

Özok, F.

Schmidt, I.

Sönmez, N.

Yıldız Technical University Research Information System

Radiation-hardness measurements of high OH- content quartz fibres irradiated with 24 GeV protons up to 1.25 Grad

WOS: 000253082000003We investigated the darkening of two high OH- content quartz fibres irradiated with 24 GeV protons at the Cern PS facility IRRAD. The two tested fibres have a 0.6 mm quartz core diameter, one with hard plastic cladding (qp) and the other with quartz cladding (qq). These fibres were exposed at about 1.25 Grad in 3 weeks. The fibres became opaque below 380 nm and in the range 580-650 nm. The darkening under irradiation and damage recovery after irradiation as a function of dose and time are similar to what we observed with electrons. The typical attenuation at 455 nm are 1.44 +/- 0.22 and 2.20 +/- 0.15 dB/m at 100 Mrad for qp and qq fibres, respectively. The maximum damage recovery is also observed near this wavelength. (c) 2007 Elsevier B.V. All rights reserved

Radiation-Hardness Measurements of High $OH^{-}$ Content Quartz Fibres Irradiated with 24 GeV Protons up to 1.25 Grad

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Ege University Institutional Repository

Radiation-Hardness Measurements of High OH−OH^{-}OH− Content Quartz Fibres Irradiated with 24 GeV Protons up to 1.25 Grad

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Radiation-Hardness Measurements of High $OH^{-}$ Content Quartz Fibres Irradiated with 24 GeV Protons up to 1.25 Grad