Quartz fibers for ECAL calibration system

The existing LED system: fibers to be replaced to more rad hard ones (quartz). Total of ~ 40 km to be purchased. LEDs to be replaced to green or blue ones (also, they should be more stable than existing red ones) LED drivers, PIN diodes amplifiers, power supplies can be kept (with maybe little modifications)

We received: from DRAKA  105/125µm fiber (pure-silica core/F-doped cladding) + acrylate coating;  100/170µm fiber (F-doped silica core/F-doped cladding) + acrylate coating;  200/230µm standard fiber(F-doped silica core/hard polymer cladding) + acrylate coating. For the light isolation DRAKA proposed to cover fibers by a black paint. (price quote: 0.74 Euro/m) from RUSSIA  200/212µm fiber (pure-silica core/F-doped cladding) + Cu foil;  200/212µm fiber (pure-silica core/F-doped cladding) + Cu/Al alloy foil; (price quote: 2.0 CHF/m)

for Ø100µm fiber & blue LED: HV=650V; max. signal ~ 600…700 adc counts; HV=1000V; max. signal overflow. Core diameter of 100µm is already enough for ECAL calibration system. Light injection test results:

Old design We need to use the existing optical connectors UNIPLAST, Vladimir, Russia

Proposal for fiber fixation

Bend Radius for core/cladding/coating (105µm/125µm/250µm)

PLANS: Production of one bundle(9 or 16 fibers), mount on ECAL, perform tests. Irradiation tests in Protvino( April 2013) with signal monitoring during irradiation.

Backup

Radiation hardness of quartz fibers

Quartz fibers as active elements in detectors for particle physics Nural Akchurin and Richard Wigmans Citation: Rev. Sci. Instrum. 74, 2955 (2003); doi: / View online: View Table of Contents: Published by the American Institute of Physics.

The OH − (hydroxide ion) content of the core affects the optical transmission and it is formulated at the preform stage. Low OH − fibers have very low attenuation throughout the infrared range from 700 to 1800 nm, except for a small absorption band at 1380 nm. On the other hand, fibers with a high-OH − core perform significantly better in the near ultraviolet region and are more radiation resistant. There are two generic types of cladding. In all-fused silica fibers, the lower refractive index region is created by doping the outer surface of the preform from which the optical fiber will be drawn. In this review, we refer to this as quartz–quartz (QQ). In the case of polymer-clad fibers, a lower refractive index material is applied around the core during the fiber drawing process (quartz-plastic) (QP).

FIG. 24 The induced in situ attenuation profile measurement for a high- OH − QP fiber at 0.54 MGy shows enhanced attenuation in the shorter wavelengths and a strong absorption peak around 610 nm. Figure. 24 shows a typical radiation-induced attenuation profile for a high- OH− QP fiber when irradiated with 500 MeV electrons. There is enhanced absorption for wavelengths <380 nm, so-called UV tail, a relatively shallow dip around 450 nm, and a strong absorption peak around 610 nm. For most quartz fibers, the optical transmission loss at 450 nm amounts to 20%–40% for an absorbed dose of 1 MGy. This wavelength is of particular importance, since most generic photomultiplier tubes have a good quantum efficiency in this region. Interestingly, the wavelength range where PMTs are most sensitive is at the same time the most radiation hard spectral region of these quartz fibers. This is a very fortunate coincidence indeed. QP type

The radiation-induced attenuation (A) depends both on the accumulated dose (D) and on the wavelength (λ). This dependence is usually expressed in the form of a power law: A(λ,D)=α(λ)*(D/D0) β(λ), Where α and β are parameters that describe the radiation hardness properties of a given type of fiber, and D0 is the reference dose. For convenience, we will chose D0 to be 1 MGy, so that at that value, α represents the induced attenuation. When similar high- OH − quartz fibers were irradiated, α values were found to range from 1.3 to 1.6 (dB/m) at 450nm. The β parameter varied between 0.2 and 0.4. In the case of the dose of 2 MRad: A(λ,D)=0.21 (dB/m) or 5%/m attenuation. In the case of the dose of 0.4 MRad: A(λ,D)=0.11 (dB/m) or 2.5%/m attenuation. In the case of the dose of 0.04 MRad: A(λ,D)=0.04 (dB/m) or 1%/m attenuation. QP type

Multi-mode hard-clad optical quartz fiber (600/660/800 µm) QP type

RIA strongly decreases with decreasing dose rate!

It was found that the dose rate has a significant effect on the optical transmission loss. At 1MRad, for example, the transmission loss is 5 % if the dose rate is 7Rad/s, whereas the loss increases to 25 % if the dose rate is 10 kRad/s at 450 nm. Clearly, the rate at which dose is delivered to the fiber plays a significant role in the dynamics of the color center formation and recovery. QP type

dB/100m QQ type Example of RIA for Draka SRH-MMF at 1300nm under dose rate of 1.25Gy/s up to 2MGy at 45°C

Radiation damages an optical fiber in many different ways. There are many different types of color centers known to exist in irradiated and un-irradiated fibers. A center, or color center, is a lattice defect in a crystalline solid consisting of a vacant negafive ion site and an electron bound to the site. Such defects will absorb light and make certain, normally transparent, crystals appear colored. This means that the light transmitted may differ in wavelength from the input light due to a color center's presence. The so-called E'-center, comprising a silicon atom with valence electrons, forms upon a radiation induced breakage of the Si-O-Si chain and is characterized by luminescence at 450 nm in addition to the absorption band at 212 nm. There is the non-bridging-oxygen radiation defect (NORD), also known as non-bridging-oxygen hole center (NBOHC), which exhibits strong absorption bands at 260 and 630 nm and has a luminescence line at 670 nm.

-105/125µm fibre (pure-silica core/Fluorine doped cladding) + acrylate coating. -100/170µm fibre with Fluorine doped core / Fluorine doped cladding + acrylate coating. -standard PCS fibre (200/230/500µm) Fiber samples from DRAKA