Bencze, G L

Fenyvesi, A

Kérek, A

Molnár, J

Norlin, L O

Novák, D

Raics, P

Szabó, Z

Szillási, Z

CERN Document Server

Radiation Tolerance Tests of CMOS Active Pixel Sensors used for theCMS Muon Barrel AlignmentBencze, Gy. L.3 Fenyvesi, A.2 Kerek, A.4 Norlin, L-O.4 Molnár, J.2 Novák, D.2Raics, P.1 Szabó, Zs.1 and Szillási, Z.11 Institute of Experimental Physics, Debrecen University, Debrecen, Hungary2 Institute of Nuclear Research (ATOMKI), Debrecen, Hungary(jmolnar@atomki.hu)3 Institute of Particle and Nuclear Physics, Budapest, Hungary and CERN,  Geneva, Switzerland4 Royal Institute of Technology (KTH), SCAFAB, Stockholm, SwedenAbstractNeutron and proton irradiation tests were performed tostudy the radiation induced alterations of COTS(Commercially available Off The Shelf) CMOS active pixelsensors at two facilities. The sensors will be used for the CMSBarrel Muon Alignment system. Results of the tests arepresented in this paper.I. INTRODUCTIONPerformance of the CMS detector of the Large HadronCollider (LHC) is affected by the position and orientation ofthe individual detectors. Therefore, the CMS detector has analignment system that consists of several subsystems. One ofthem is the  barrel and end-cap internal alignment, whichmeasures the positions of the muon detectors with respect tothe linking points [1]. This system will consist of LEDlight-sources, the related electronics and video camerasequipped with video-sensors (~ 800 pcs) [2].The light sources will be attached mechanically to themuon chambers and its operation is controlled remotely. Thevideo cameras are fixed to a rigid grid structures whichpositions are calibrated by a laser link system. The imagesfrom the cameras are digitised and evaluated by 36 pcsdedicated PC104 type board computers. The board computerscalculate the co-ordinates of the LEDs on the images and sendthose values to the Supervisory Control and Data Acquisition(SCADA) workstation.The optical and opto-electronic components have to workin a radiation environment, where the expected neutronfluence is 2.6E12 n/cm2 and the expected proton fluence is1E11 p/cm2. Radiation damage induced by neutrons andprotons can alter electrical and optical characteristics of thecomponents and thus the accuracy of the whole alignmentsystem.II. EXPERIMENTAL TECHNIQUESA. Image sensorVideo cameras based on the VM5402 CMOS ImageSensor have been selected and tested for surveying thealignment of the CMS Barrel Muon detector system. TheVM5402 manufactured by VISION is an active pixel typeimage sensor with 388 x 295 pixels, each with an area of12 x 12 mm2. The module is suitable for applications requiringa composite video signal with minimum external circuitry [3].The photo of the camera can be seen in figure 1.Figure 1: Video camera based on the VM5402 CMOS ImageSensorB. Radiation facilitiesFive samples of camera have been tested with 20 MeV and95 MeV neutron and 98 MeV proton beams with fluencescorresponding to the radiation environment calculations.The 95 MeV neutron beam was produced at the GustavWerner Cyclotron facility of the The Svedberg Laboratory(TSL) in Uppsala by 98 MeV proton beam hitting an 8 mmLi-target.The 20 MeV neutron irradiation was done at the neutronirradiation facility at the MGC-20E cyclotron at ATOMKI,Debrecen with p(20MeV)+Be reaction [4]. Neutrons with abroad spectrum (En<20MeV, <En>=3.5MeV) were producedby bombarding a 3 mm thick target by protons.The 98 MeV proton beam of the TSL cyclotron wasbroadened by a scatterer and was extracted to air[5].C. Image recordingThe video signal from the camera during irradiation wasstored using a standard video recorder. In each second 50images were recorded for off-line analysis.III. RESULTS AND DISCUSSIONSThe recorded video images of the irradiation showed whitespots and long tracks which were results of the differentnuclear interactions caused by the proton and neutronirradiation. The heavy fragments from the nuclear reactionswere observed as white spots in the image. The light chargedparticles like protons and alpha particles that follows thenuclear reactions are emitted with different energies anddirections, according to the kinematics of the process. Some ofthese particles were emitted in the sensitive plane of theCMOS Image Sensor. They deposit their energy to the siliconand the released charge, forming the tracks, are detected bythe pixels. These tracks are visible on the video image. Thecharge is registered along the track and the intensity value ofthe signal can be analysed off-line.In figure 2 a camera image recorded during 98 MeVproton irradiation can be seen. The smaller white round spotsare the result of the heavy charged particles. The largest roundwhite spot close to the longest track is the light from the LED.In figure 3 clearly visible the “background” created by thedirect ionisation of the radiation. The greyscale level in pixelswhere no flash was detected increased when the beam was on.This can be explained by the effect of the direct ionisation ofthe protons. Majority of the protons does not make a nuclearreaction in the silicon of the image sensor, but loses a certainamount of energy by direct ionisation. The sum of these smalldeposited energies forms the special background structure.The products of two reactions can also be seen. In one of thereactions both the heavy fragment (large spot) and a lightfragment (long track) can be seen.The phenomena in the camera can be called a “visibleSingle Event Phenomena (SEU)”. Because of the analognature of the image sensor the result of the SEU can be seen inmore detail compared to a digital circuit.Figure 2: A typical image during 98 MeV proton irradiation.Figure 3: Image presenting the background structure caused by theirradiation.The incident light creates proportional charges in theactive pixels and this charge forms the image visible on thevideo monitor. In the described experiment the charges in thesensor are generated by the energy deposited by the heavy andlight charged particles. Consequently the image seen on themonitor is the direct effect of the charged particles.One possible reaction that can take place in the silicon ofthe image sensor is presented in figure 4. The heavy reactionproduct (25Al) leaves on the average 2 MeV/mm. If this energyis deposited in the sensitive volume of the sensor, a spotoccurs on the image. Because of the short range of the heavyfragment the deposited energy forms a round spot on theimage. The range of the light fragment (a particle) is ratherlong, so a long track is its image. The reaction in figure 4 is apossible candidate for the reaction in figure 3 where a longtrack originates from a spot. The deposited energy along thetrack follows the Bragg curve, this is the reason why the longtrack becomes broader and brighter towards the end of thetrack (close to the edge of figure 3.).It is obvious that a nuclear reaction caused by a proton or aneutron is a complex process. than the traditional SEU that iscaused by a heavy ion. The lack of experimental informationurge for investigation of the nuclear reaction processes insilicon with focus on the rare channels that produce highlyionising secondary fragments. The range of the nucleon-induced heavy secondary ions is comparable to the size of thestructure in an IC. This is illustrated in the figure 4 belowwhere one, out of many possible reactions in silicon is shown.Figure 4. A schematic figure describing one of all of the possibleoutcomes of a proton induced nuclear reaction with 28Si.In a previous experiment [7], a silicon detector was used asan active target and particle telescopes detected light chargedreaction products like p, d, t, 3He and a-particles. The heaviestfragments in such nucleon-initiated reactions are responsiblefor the SEU’s but due to their short range in silicon they couldonly indirectly be detected via the associated light fragment.One could compare these findings with standard SEU crosssection measurements for selected memories with knowncircuit topology. The method and the first tests were reportedrecently [7]. The results obtained were compared andinterpreted with Monte Carlo simulations using the GEANTcode. From this exploratory experiment one can conclude thata large number of charged particles are released in the reactionand that the Monte-Carlo simulation gave, when it wasapplicable, a reasonable agreement with the measured data.IV. CONCLUSIONThe video cameras based on the VM5402 CMOS ImageSensor intended to be used in the CMS Muon BarrelAlignment system was studied with protons and neutrons. Theobserved effects caused by the radiation can be tolerated in theBarrel Muon Alignment system. However special care has tobe taken during the calculation of the LED positions becausethe image is relatively heavily effected by the tracks and spotsproduced by the radiation field.V. ACKNOWLEDGEMENTThis work was supported in part by the HungarianScientific Research Fund (OTKA T026184 and OTKAT034910).VI. REFERENCES[1] CMS – The muon project. Technical Design Report.CERN/LHCC 97-32.[2] L. Baksay, P. Raics, Zs. Szabó, L. Molnár, G. Pszota, A.Fenyvesi, J. Molnár, Gy. L. Bencze, L. Brunel, D.Novak: Neutron radiation tolerance tests of optical andopto-electronic components for the CMS Muon BarrelAlignment, Presented at the 7th Workshop on Electronicsfor LHC Experiments, Stockholm, Sweden, September2001, CERN/LHCC/2001-034, (2001).[3] VISION VM 5402 Camera Module datasheet.[4] A. Fenyvesi, I. Mahunka and T. Molnar, Zeitschrift fürMedizinische Physik, 1, 1 (1991) 30-32.[5] O. Jonsson, P.-U. Renberg, A. Prokofiev, A. Smirnov, Abroad-proton-beam facility for irradiation purposes,TSL progress report 1998-1999. [6] A. Sipos, E. Grusell, A. Kerek, W. Klamra, J. Molnár,L.-O. Norlin, D. Novák, A. Sanchez-Crespo, J. Van derMarel and J. Végh: Visualization of Neutron and ProtonInduced Particle Production in a CMOS Image Sensor,To be presented at the IWORID 2002 conference,Amsterdam, The Netherlands. [7] D. Novák, A. Kerek, W. Klamra, J. Molnár, J. Van derMarel, L.-O. Norlin, J. Nyberg and P.-U. Renberg, Acomparison of experiment and simulation of lightparticle production in silicon  by 74 MeV neutrons.Presented at RADECS 2001, Grenoble,  and acceptedfor publication in IEEE Trans. Nucl. Sci.16 MeVrange: 7 mmggg25Al75 MeVrange: 2.2 mma100 MeVp28Si

Radiation tolerance tests of CMOS active pixel sensors used for the CMS muon barrel alignment

Radiation tolerance tests of CMOS active pixel sensors used for the CMS muon barrel alignment

Abstract

Similar works

Full text

Available Versions

CERN Document Server