Fig 19 full#
Fig 19 Pc#

Counting rate is measured below 1 kHz in a laboratory at low altitude. Counting rate refers to the signal rate that exceeds threshold of electronics, which is mainly contributed by the minimum ionization particle (M.I.P.) signal, dark noise of PMT and background radiation. The detection efficiency is measured by the telescope system with muons triggering ( Fig. Time resolution of the telescope is known and therefore the ED time resolution can be extracted (see Fig. The width of distribution of difference between them includes time resolutions of ED and the telescope. For the time resolution measurement, hit times of ED are compared with the one of the telescope trigger system. Uniformity of Single particle peak of one ED is shown in Fig. Photo-electrons (p.e.s) are proportional to the charge measured, which is extracted from the peak. Single particle charge spectrum is acquired and fitted with the convolution of Landau with a Gaussian function ( Fig. Table 2. Performance test results of the unit ED. Together with detection units, electronic system and power supply system, a temperature and humidity monitoring system is also installed inside the detector shell. The PMT and FEE are powered by the same power supply, but the high voltage of PMT can be adjusted independently.

Fig 19 full#

The ED FEEs also allow to measure charge with high precision on the full scale array. With help of the White Rabbit clock system, the FEEs of the different EDs are synchronized among them with a precision of 500 ps. Stable operation are guaranteed for temperature ranging from −35☌ to 55 ☌. Charge accuracy is 3% for 1 particle and 1% for 10 4 particles, and time accuracy is 0.5 ns.

Fig 19 Pc#

Anode charge measurement ranges from 0.64 pC to 256 pC, and for dynode ranges from 0.32 pC to 128 pC. Data contains arrival time information of hits, accurate charge information, slow control, register feedback, etc. 7) where each detector has a local front-end electronics (FEE) for signal digitalization and data transmission to the Data Acquisition (DAQ) system. The ED electronics system adopts a trigger-less, independent, front-end digitization scheme (see Fig. PMT is wrapped in a magnetic shielding film of permalloy to reduce the influence of geomagnetic field.

The temperature coefficient is less than 0.2%/☌. Ratio of anode current to dynode current is around 110.

To achieve the large dynamic range required (4 orders of magnitude), an optimal design of the voltage divider with anode and the 6th dynode readout has been developed. 6 (color online) Photo of an installed ED. KM2A will reach a sensitivity of about 1% of a Crab-like source for energy of 100 TeV in one year of observation. For gamma ray detection, KM2A has following performance: effective area can reach 0.8 km 2 at 30 TeV, angular resolution isĪt 1 PeV, core position resolution is 7 m at 30 TeV and 2 m at 1 PeV, and energy resolution is 28% at 30 TeV ( Fig. An array on muon detectors (MD), each having a surface area of 36 m 2, is also deployed on the same areas arranged on a triangle grid of 30 m spacing, to form together with the ED array, the KM2A. This will be achieved in LHAASO, by a precise measurement of the muon component of the shower, which will be extremely effective in suppressing the background. At the same time, above 50 TeV, it is essential to have a background-free sample of gamma rays, i.e. In order to achieve threshold energy of 30 TeV and angular resolution of few tenths of degree, the area has to be equipped with electromagnetic detectors of about 1 m 2 arranged on a triangle grid with spacing of 15 m. Therefore to have reasonable effective area for this fluxes, it is necessary to instrument a geometrical area of about 1 km 2 to measure extensive air showers (EAS) generated by cosmic rays in atmosphere. One square kilometer array will detect about 1000 gamma rays above 100 TeV from the Crab-like source and then 10 gamma rays from a source with a flux of 1% of the Crab-like source in one year. Considering the location of LHAASO, the effective observation on the Crab-like source, i.e., the source with same position and same spectral shape with Crab Nebula, is 6.5 hours per day. Above 100 TeV, the flux of the Crab-like source is 0.45 gamma rays per km 2 per hour.