Transmittance Measurements of VUV Light as a Function of Water Vapor and Oxygen Concentrations PHENIX Experiment, Brookhaven National Laboratory June - July 2004 G. Karagiorgi**, B. Azmoun*, C. Woody*, M. Hohlmann** *Brookhaven National Laboratory **Florida Institute of Technology Hello, my name is…. I am going to be talking about …. This was a study performed for the PHENIX experiment at BNL and it was performed over this last summer by myself, B. Azmoun and… Florida Academy of Sciences 69th Annual Meeting Tampa, FL March 18, 2005

Purpose of Study: Reference for the Hadron Blind Detector (HBD), which is going to be employed at the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) facility, at Brookhaven National Laboratory. The purpose of the study was to provide a reference for optimum operation conditions for the HBD detector, which is a gas Cherenkov detector. This detector is currently under construction and it is going to be employed… by the end of year 2005 Reference: http://www.phenix.bnl.gov/ Georgia Karagiorgi, FAS 2005

Introduction: Gas Cherenkov Detectors Detection of Cherenkov light v > c/n in medium (refraction index n) β = c/v cosφ=1/nβ Reference: http://encyclopedia.thefreedictionary.com/Cherenkov%20effect A gas Cherenkov detector is a detector which is based on detection of Cherenkov light. Cherenkov light is produced when an energetic particle travels through a medium (here, gas) at a speed that is faster than the speed of light in the medium. It is basically the same effect as a sonic boom, which occurs when an object travels in air faster than the speed of sound in the medium. The HBD detected the cherenkov light that is produced by lepton pairs and it falls. This light is in the violet-ultra violet region of the light spectrum. Factors that HBD  Violet – Ultraviolet (VUV) light detection Georgia Karagiorgi, FAS 2005

Introduction: Gas Cherenkov Detectors: VUV Transmittance factors: Gas Type ( radiator, transparent to desired λ ) Out-gassing ( vessel material ) Contaminant particles ( N2 , O2 , H2O vapor ) Georgia Karagiorgi, FAS 2005

Study: Transmittance of VUV light as a function of H2O vapor and O2 concentrations Reference for water and oxygen levels that can be tolerated within such a detector before any significant fraction of VUV light is lost % Transmittance of VUV light in Ar gas vs. H2O [ppm] % Transmittance of VUV light in Ar gas vs. O2 [ppm] This specific study was intended to act as a reference for water and oxygen levels that can be tolerated within such a detector before any significant fraction of VUV light is lost. %T = (Flux out / Flux in)*100% Georgia Karagiorgi, FAS 2005

Method: Experimental Setup sample i vacuum Reference: http://www.phenix.bnl.gov/phenix/WWW/publish/azmoun/Trans_O2_H2O.pdf Georgia Karagiorgi, FAS 2005

Theory: Theoretical Transmittance I(x) = Io e -μx I(x=L) = Ioe –σNL I(x=L) = Ioe –σpNL I(x) : flux after the beam has traversed a distance x trough the absorber Io : initial flux μ : attenuation coefficient N : particle density (particles per cubic cm) L : total length through which the VUV beam travels σ : interaction cross section Interaction cross section, [Mbarn] Vs wavelength [Angstroms] for H2O Reference: A.N. Zaidel’ and E.Ya. Shreider, Vacuum Ultraviolet Spectroscopy. Ann Arbor-Humphrey Publishers; Ann Arbor, London 1970 Attenuation coefficient, µ [cm-1] Vs wavelength [Angstroms] for O2 I(x) is the flux after the beam has traversed a distance x trough the absorber I0 is the initial flux Μ is the attenuation coefficient N is the particle density (particles per cubic cm) L is the total length through which the VUV beam travels Σ is he interaction cross section Reference: A.N. Zaidel’ and E.Ya. Shreider, Vacuum Ultraviolet Spectroscopy. Ann Arbor-Humphrey Publishers; Ann Arbor, London 1970 Georgia Karagiorgi, FAS 2005

Results: Transmittance in H2O vapor Plot 1: Transmittance spectra as a function of H2O levels Interaction cross section, [Mbarn] Vs wavelength [Angstroms] for H2O Reference: A.N. Zaidel’ and E.Ya. Shreider, Vacuum Ultraviolet Spectroscopy. Ann Arbor- Humphrey Publishers; Ann Arbor, London 1970 Georgia Karagiorgi, FAS 2005

Results: Transmittance in H2O vapor Plot 2: Transmittance data @1290 Angstroms Vs H2O levels, compared to the expected transmittance--calculated from the interaction cross section @1290s Angstrom, extracted from the theoretical data for attenuation coefficient. Georgia Karagiorgi, FAS 2005

Results: Transmittance in O2 Plot 3 Transmittance spectra as a function of O2 levels Attenuation coefficient, µ [cm-1] Vs wavelength [Angstroms] for O2 Reference: A.N. Zaidel’ and E.Ya. Shreider, Vacuum Ultraviolet Spectroscopy. Ann Arbor- Humphrey Publishers; Ann Arbor, London 1970 Georgia Karagiorgi, FAS 2005

Results: Transmittance in O2 Plot 4: Transmittance data @1450 Angstroms Vs O2 levels, compared to the expected transmittance--calculated from the attenuation coefficient @1450 Angstroms, extracted from the theoretical data for attenuation coefficient. Georgia Karagiorgi, FAS 2005

Conclusions In agreement to previous experimental data Provided reference for tolerable contaminant levels for efficient operation of the HBD detector Determined the necessity for good sealing Georgia Karagiorgi, FAS 2005

References A. N. Zaidel and E. Ya. Shreider. Vacuum Ultraviolet Spectroscopy. Ann Arbor Humphrey Publishers; Ann Arbor, London; 1970. B. Azmoun, G. Karagiorgi and C. Woody. Transmittance as a function of water and oxygen levels in the VUV regime. September, 2004. http://www.phenix.bnl.gov/phenix/WWW/publish/azmoun/Trans_O2_H2O.pdf http://www.phenix.bnl.gov http://www2.slac.stanford.edu/vvc/detectors/cerenkov.html Georgia Karagiorgi, FAS 2005