Study of Cosmic Rays Profgesor: Mario Edoardo Bertaina Students: Morari Eugen Gramă Vasile
Objectives 1 What are cosmic rays? Origins of Cosmic Rays & Compositjon 2 3 3 Scintjllators & Photomultjplyers CORSIKA (COsmic Ray SImulatjons for KAscade) 4 4 Measurement chain (ADC, TDC, DISCRIMINATOR) 5 Efjcience dependence 6 7 Results & Conclusions
Cosmic Rays • Cosmic rays are high-energy radiatjon, mainly originatjng outside the Solar System and even from distant galaxies. Upon impact with the Earth's atmosphere, cosmic rays can produce showers of secondary partjcles that sometjmes reach the surface.
Particles in the atmosphere
Compositjon Of primary cosmic rays, which originate outside of Earth's atmosphere, about 99% are the nuclei of well-known atoms (stripped of their electron shells), and about 1% are solitary electrons (similar to beta partjcles). Of the nuclei, about 90% are simple protons (i.e., hydrogen nuclei); 9% are alpha partjcles, identjcal to helium nuclei; and 1% are the nuclei of heavier elements, called HZE ions. A very small fractjon are stable partjcles of antjmatuer, such as positrons or antjprotons. The precise nature of this remaining fractjon is an area of actjve research. An actjve search from Earth orbit for antj- alpha partjcles has failed to detect them.
Primary Cosmic Ray
Shower
Calculations
2D Plan Project
EAS – array - roof
Aparatus SCINT - MTEL
MRPC - MTEL
Measurement chain The signal coming from each detector is taken via cables to the reading electronics on the floor of the building; the signal then passes into an amplifier which has two simplified outputs and is simultaneously split; the first signal is discriminated and is in turn split into two signals, of which the first is delayed and provides the stop of the TDC, while the second is sent to the
Chain of measurement: discriminator Input: analog signal Discrimination threshold Output: logic signal when the threshold is exceeded
Measure chain: TDC Time to digital converter Measure the differences between the arrival times of the particles in the different scintillators. From these we get the direction of arrival
Measurement chain: qADC Measure the charge of analog signals in time given by a "gate" (logic signal) It tells us "how big" is a signal, Proportional to n. of particles that pass through the scintillator
TDC calibration • During this part of the experience the measurements were made setting 1000 events for acquisition because it has been observed that a delay equal to 1 ns corresponds to 4 channels on the TDC spectrum. • The operation was repeated on channels 1 and 2, progressively varying the length of the delay through the removal of signal cables and relative connecters and a first comparison was made between the average TDC values obtained at the time and in the acquisition phase of individual events. • The start of the TDC has been delayed by using three signal cables, which each provide a time delay equal to 15 ns and are connected to one another by means of conectors, each furnishing a delay equal to 0,5 ns.
Calibration and verifjcation of TDC linearity • TDC (Time to Digital Converter): determines the tjme interval between two signal pulses (start and stop signal). The measurement is started and stopped when the rising or falling edge of a signal exceeds a certain threshold • The calibratjon procedure consists in introducing a known delay to the start or stop signal using a cable whose length determines a signal delay of 15 ns (travel tjme of 5 ns / m for 3 m)
Measures verify the linearity of the TDC • The linearity of the TDC response is verifjed by applying increasingly large delays to the stop signal (from 3ns to 41 ns) • The delays are obtained by gradually connectjng difgerent cables using I- connectors. • For each delay, start and stop value, 1000 events were acquired • The fjgure shows the results obtained through linear fjt
Angular distribution of the beam according to the angle θ The swarm incidence directjons can be derived from the data obtained from the TDC. The angular distributjon follows the following law: y = p 0 sin (θ) cos (θ) and -p 1 / cos (θ) p 0 is proportjonal to the number of incident events. p 1 = x 0 / λ x 0 = radiatjon length defjned as the average distance in which a partjcle remains with an energy equal to 1 / e. λ = average thickness of the atmosphere crossed by the partjcle.
Angular distribution of the beam according to the angle Φ • The angular distributjon in Φ is essentjally fmat and confjrms the hypothesis of isotropic irradiatjon. • That is how the swarms of partjcles afgect the detectors from every directjon (Φ), while the inclinatjon (θ) of the swarm with respect to the vertjcal follows a well-defjned distributjon.
Center of gravity From the fjgure we can see that these events are distributed in a rather isotropic way around the point of coordinates L (½, ½, 0) The distributjon obtained is in line with that expected around the central detector There is a slight anisotropy due to: 1) the 5 statjons in concrete do not form a perfect square; 2) the scintjllator 2 is not very effjcient; 3) the scintjllator 5 operates at a higher voltage than that set during the data socket
Detecting cosmic rays • If a charged partjcle (e.g. a cosmic ray) passes through all the scintjllators, it will produce an electrical pulse from each. • If these signals occur almost exactly a the same tjme, we assume that these “coincidences” have been produced by a charged partjcle passing through scintjllators. • The electronics counts how many coincidences have been detected. • This counter tells us directly how many cosmic rays have passed through the fjve scintjllators in a given tjme.
Scintillator • A scintjllator is a material that exhibits scintjllatjon—the property of luminescence, when excited by ionizing radiatjon. Luminescent materials, when struck by an incoming partjcle, absorb its energy and scintjllate, (i.e. re-emit the absorbed energy in the form of light).Sometjmes, the excited state is metastable, so the relaxatjon back down from the excited state to lower states is delayed (necessitatjng anywhere from a few nanoseconds to hours depending on the material): the process then corresponds to either one of two phenomena, depending on the type of transitjon and hence the wavelength of the emitued optjcal photon: delayed fmuorescence or phosphorescence, also called afuer-glow.
Scintillator
Photomultiplier • Photomultjplier tubes = members of the class of vacuum tubes, and more specifjcally vacuum phototubes, are extremely sensitjve detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetjc spectrum. These detectors multjply the current produced by incident light by as much as 100 million tjmes (i.e., 160 dB), in multjple dynode stages, enabling (for example) individual photons to be detected when the incident fmux of light is low.
CORSIKA (COsmic Ray SImulatjons for KAscade) CORSIKA is a program for detailed simulatjon of extensive air showers initjated by high energy cosmic ray partjcles the partjcles are tracked through the atmosphere untjl their energy decreases below a certain threshold (because of reactjons with the air nuclei or decay) into this program all the known processes that infmuence physical parameters of a shower are included
Commands: • cd /mnt/data27/corsikagv/corsika-75600/run$ • source ../source_me.bsh • ./corsika75600Linux_QGSII_fmuka < all-inputs123 • ls –lh DAT000123 • ls DAT000123 > inputDAT000123 • ./corsikaread.exe < inputDAT000123 • ls fort.7 –lh • mv fort.7 fort.7_DAT000123 • root • .L test3.C • test3(“fort.7_DAT000123”) • p: ibrahimovich97 • U: vasile….
Input fjle
Positions of detectors
Surface
Lateral distribution of a single event (KASCADE- Grande)
Results The sum of the last triggers is: 0.75 events/min
Conclusions We have seen that charged partjcles fmy from the universe into our atmosphere where they collide with air molecules producing air showers. We have also seen how measuring the secondary partjcles gives informatjon about the primary partjcle and how special relatjvity explains that briefmy living partjcles can stjll reach the earth because of their slow running proper tjme. Cosmic rays happen to consist for about 86% out of protons.
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