Calibration of photomultiplier using UVLED

Detector calibration is very important for the long-term operation. For the purposes of simple and precise calibration, we developed a new portable calibration source using UVLED to calibrate the fluorescence detector of the Telescope Array experiment (TA). The UVLED is light (less than 1 kg) and its setup is quick and easy. Therefore, a single source will be used instead of the calibration sources that TA currently uses. The UVLED emits 369 nm wavelength and ~70 pJ of photons which are calibrated with 5% accuracy us-ing photo-diode. It has a particular unit, which is an internal heater, to keep the temperature constant and avoiding temperature dependency on light yield. The first result of calibration for 24 detectors is xx pho-tons/faced count for 369 nm photons with 6% uncertainty. It is in agreement with the result of the current calibration sources of TA

A non-destructive correlated energy spread monitor using multi-stripline electrodes for X-ray free electron lasers

During X-ray free electron laser (XFEL) operation, electron beam parameters such as the correlated energy spread, which affects the self-amplified spontaneous emission (SASE) spectrum, should remain optimized for the best performance. However, the correlated energy spread often varies from the optimized condition owing to the drift of RF stations, even when a feedback system with low-level radio frequency is operating. Non-destructive correlated energy spread monitoring could offer a means to stabilize such variations and improve the performance of X-ray generation by maintaining the spectral quality. Herein, we investigated the feasibility of a non-destructive correlated energy spread monitor based on multi-stripline electrodes for use with the 200 pC electron beam at the Pohang Accelerator Laboratory XFEL (PAL-XFEL). Beam tracking and electromagnetic simulations indicated that the correlated energy spread up to approximately 0.1% could be measured without intercepting the beam at the bunch compressors of the PAL-XFEL. Through the 3D FEL simulation, we confirmed that keeping the SASE energy spectrum bandwidth to 0.05-0.15%, with a photon energy of 9.7 keV at the undulator, requires the correlated energy spread of the electron beam to be within 0.12-0.35% at the third bunch compressor. From the simulations, we conclude that the non-destructive correlated energy spread monitor based on multi-stripline electrodes is applicable to XFEL facilities and could serve as an effective optimization tool

Observation of radio emissions from electron beams using an ice target

To observe high energy cosmogenic neutrinos above 50 PeV, the large neutrino telescope ARA is being built at the South Pole. The ARA telescope detects neutrinos by observing radio signals by the Askaryan effect. We performed an experiment using 40 MeV electron beams of the Telescope Array Electron Light Source to verify the understanding of the Askaryan emission as well as the detector responses used in the ARA experiment. Clear coherent polarized radio signals were observed with and without an ice target. We found that the observed radio signals are consistent with simulation, showing that our understanding of the radio emissions and the detector responses are within the systematic uncertainties of the ARAcalTA experiment which is at the level of 30%

Probing the radar scattering cross-section for high-energy particle cascades in ice

Recently the radar scattering technique to probe neutrino induced particle cascades above PeV energies in ice was investigated. The feasibility of the radar detection method was shown to crucially depend on several up to now unknown plasma properties, such as the plasma lifetime and the free charge collision rate. To determine these parameters, a radar scattering experiment was performed at the Telescope Array Electron Light Source facility, where a beam of high-energy electrons was directed in a block of ice. The induced ionization plasma was consequently probed using a radar detection set-up detecting over a wide frequency range from 200 MHz up to 2 GHz. First qualitative results of this experiment will be presented.SCOPUS: cp.pSCOPUS: cp.pinfo:eu-repo/semantics/publishe

Study of Microwave Radiation from the Electron Beam at the Telescope Array Site

International audienceThe Telescope Array (TA) experiment installed the electron accelerator in order to calibrate the fluorescence detector by shooting 40 MeV electrons into the atmosphere. This accelerator also works to investigate the radio detection techniques used for the cosmic ray observations. Using this accelerator, four experimental groups have studied individual radio detection methods at different frequency bands ranging from 50 MHz to 12 GHz. All of these experiments have observed the microwave radiation from the electron beam itself. We have studied the radiation by combining all the measured results and constructed a model of this phenomena. Results of four experiments and model expectation are in good agreement within the systematic uncertainty

Coherent radio emission from the electron beam sudden appearance

International audienceWe report on radio frequency measurements of the electron beam sudden appearance signal from the Telescope Array Electron Light Source (TA-ELS). The TA-ELS is constructed to calibrate the Telescope Array fluorescence telescope, and as such it can be used to mimic a cosmic-ray or neutrino induced particle cascade. This makes the TA-ELS the perfect facility to study new detection techniques such as the radio detection method. We report on the data obtained by four independent radio detection set-ups. Originally searching for either the direct Askaryan radio emission, or a radar echo from the induced plasma, all these experiments measured a very strong transient signal when the beam exits the accelerator. Due to the different scope of the individual experiments, we have detected the beam sudden appearance signal at different frequencies, ranging between 50 MHz and 12.5 GHz. The direct application in nature for this signal is found in cosmic-ray or neutrino induced particle cascades traversing through different media, such as air, ice, and rock. These measurements are compared to the theoretical predictions for this signal, where it follows that theory and experiment match very well over the full spectrum