[show abstract][hide abstract] ABSTRACT: The fluorescence yield in air is reported for wavelength and pressure ranges of interest to ultra-high energy cosmic ray detectors. A 28.5 GeV electron beam was used to excite the fluorescence. Central to the approach was the system calibration, using Rayleigh scattering of a nitrogen laser beam. In atmospheric pressure dry air, at 304 K, the yield is 20.8±1.6 photons per MeV.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 11/2008; 175(1):472. · 1.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: A key assumption in the reconstruction of extensive air showers using
the air fluorescence technique is that fluorescence is proportional to
energy deposition at all depths in the shower. This ansatz, along with
the supposition that particle distribution and energy loss can be well
modeled by modern shower simulation software, must be thoroughly
verified. We report here the results of the first direct measurement of
air fluorescence yield as a function of shower depth, as performed in
the thick-target phase of the FLASH (FLuorescence in Air from SHowers)
experimental program at the SLAC Final-Focus Test Beam facility. We
compare observed fluorescence light yields as a function of shower depth
to concurrently measured charged particle yields, to the energy
deposition predictions of the EGS and GEANT software packages, and to
empirical energy-deposition models. We also examine the extent to which
the relative yield versus shower depth is independent of wavelength
within the fluorescence spectrum. We find the proportionality hypothesis
to be well supported by the data, validating the use of fluorescence
profiles in the study of ultra high energy cosmic rays.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 10/2008; 597:37-40. · 1.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: Measurements are reported of the yield and spectrum of fluorescence, excited by a 28.5 GeV electron beam, in air at a range of pressures of interest to ultra-high energy cosmic ray detectors. The wavelength range was 300 - 420 nm. System calibration has been performed using Rayleigh scattering of a nitrogen laser beam. In atmospheric pressure dry air at 304 K the yield is 20.8 +/- 1.6 photons per MeV
[show abstract][hide abstract] ABSTRACT: Measurements are reported on the fluorescence of air as a function of depth in electromagnetic showers initiated by bunches of 28.5 GeV electrons. The light yield is compared with the expected and observed depth profiles of ionization in the showers. It validates the use of atmospheric fluorescence profiles in measuring ultra high energy cosmic rays.