Project Scope

To study the viability and radiation hardness of baseline scintillating fibers for the scintillating fiber tracker upgrade.

Indico Meetings Page

Goals:

Measure the number of photoelectrons seen in one hit cluster for points along the length of the fiber module, as well as the attenuation length during foreseen LHCb upgrade design and radiation conditions.

In the short time-span of a few months, we must understand how the scintillating fibers will respond and degrade in the radiation field of the upgraded luminosity of LHCb, with respect to the particle type, fluence and integrated dose, assuming the lifespan of the detector should exceed an integrated luminosity of 50 fb^{-1}. In other studies, scintillating fiber degradation has been found to be sensitive not only to the total dose, but enviromental conditions and dose rates due to annealing effects within the polymer structure of the plastic. The absorption of light within the fiber by the free radicals in the polystyrene matrix is strongly wavelength dependent, meaning that the type of scinitillating dyes used (fiber type) is important, but we may be limited by the availablity of manufacturers. By systematically exploring these factors, we can understand fully the behavior of the fibers in the upgraded LHCb.

Projects:

1. Photoelectrons as a function of dose and/or dose rate and Attenuation length (absorption/cm/Rad ) in different regions of damaged fiber. Not just one bulk attentuation length.

a. What is the impact of environmental effects? i.e. clear epoxy, with Titanium Oxide, with carbon, temperature, air flow, Nitrogen/Oxygen atmosphere.

b. Can the damage be undone via thermal annealing, visible/UV light?

c. Are there better fibers than Kuraray SCSF78-MJ for us?

2. Signal shape and Mirroring of a 2.5 metre long fiber.

a. Do we gain from mirroring? Maybe a blackened end is better.

b. Are the reflections a hindrence or a help? Where and when?

3. Temperature considerations (down to -50C ) for the interface between the SiPM and the fibers.

a. Does the transparency/light yield change?

b. Do the fibres or glue become mechanically brittle/shrinkle/wrinkle?

Lab Facilities:

Who has what resources for fulfilling these goals?

Cern: module, SiPM readout, fibre, reflectometer, spectrometer, thin film mirror coating

EPFL: modules, SiPM and readout, fibre

Dortmund: winding wheel, 10km? of Kuraray fiber, module making facilities.

Heidelberg :

Photo-spectrometer: Hamamatsu C10083CA-2050 , Calibrated photodiode UV-818 , Calibrated Tungesten lamp Specs; Pico-ammeter: Keithley 6487 , 150m of SCSF78-MJ 0.25mm fibre. 15m samples of clear, 3HF fibre. 100m samples on order from Saint Gobain. 370nm UV-LEDs. KETEK SiPMS (wire bonded, non-epoxied)

Who else?

Irradiation Facilities:

Who has / can provide access to which facilities?

Cern : protons (24 GeV). 2 x 2 cm2 beam spot + moveable tables for larger surfaces. However no beam in 2013/14 !

PSI Swizerland: Broad range of energies and intensities of the proton beam, Experiment adaptable monitoring of flux and dose, Fast and uncomplicated experimental setup, Transparent operating procedure, User friendly data acquisition system

TSL Uppsala, Sweden: Neutron and Proton beams http://www.tsl.uu.se/irradiation-facilities-tsl/; (Anita) Neutron beam with spectrum that resembles the one in the Earth´s atmosphere, High neutron flux, >= 10^6/cm/s, Variable flux and beam spot size; (QMN) Selectable neutron energy in the 20-175 MeV energy range, Variable flux, up to 3*10^8 neutrons per second over the beam area, Variable beam spot size; (PAULA) Selectable proton energy in the 20-180 MeV energy range, variable flux, Variable uniform beam spot size

KVI Groningen, Netherlands: <190 MeV Protons (solar spectrum) http://www.rug.nl/kvi/experimentalfacilities/userfacility/index

Internal notes:

• Decay_time_const.pdf: A small study on the decay time constant of SCSF-79, before and after irradiation

Literature:

Kuraray Scintillating Fibers Website http://kuraraypsf.jp/psf/sf.html

Shortlived absorption centers in plastic scintillators and their influence on the fluorescence light yield W. Busjan, K. Wick, T. Zoufal http://www.sciencedirect.com/science/article/pii/S0168583X98009744

A pedestrian's guide to radiation damage in plastic scintillators C. Zorn http://dx.doi.org/10.1016/0920-5632(93)90049-C

Radiation Damage by Neutrons to Plastic Scintillators G. Buss, A. Dannemann, U. Holm, K. Wick http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.44.5999&rep=rep1&type=pdf

Strong Reduction of Radiation Damage in Plastic Scintillators by Illumination With Visible Light Wick, K.; Gosau, T.; Hornung, R.; Ziegler, A. http://dx.doi.org/10.1109/TNS.2005.852707

Isothermal annealing of color centers in irradiated polystyrene in vacuum and air atmospheres I.J. Chiang, C.T. Hu, Sanboh Lee http://dx.doi.org/10.1016/S0254-0584(00)00471-5

Reduction of the permanent radiation induced absorption by illumination of plastic scintillators during γ-irradiation K. Wick,R. Hornung,T. Gosau http://dx.doi.org/10.1016/j.nima.2004.09.023

Spectral response of scintillating fibers, Z. Papandreou, B.D. Leverington, G.J. Lolos,, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 596, Issue 3, 11 November 2008, Pages 338-346, ISSN 0168-9002, 10.1016/j.nima.2008.08.136.; http://www.sciencedirect.com/science/article/pii/S0168900208013119

Literature study on the radiation damage on KURARAY fibers, S.Bruggisser (EPFL), September 2012, FiberSummaryNew.pdf

-- ChristianJoram - 20-Jun-2013