Passive neutron albedo reactivity measurements of spent nuclear fuel

The upcoming disposal of spent nuclear fuel in Finland creates new challenges for nuclear safeguards. Part of the national safeguards concept for geological repositories, developed by STUK — Radiation and Nuclear Safety Authority, is non-destructive assay (NDA) verification of all fuel items before disposal. The proposed verification system is a combination of PGET (Passive Gamma Emission Tomography), PNAR (Passive Neutron Albedo Reactivity) and weight measuring NDA-instruments. PGET takes a pin-level image of the fission products inside of a fuel assembly and PNAR verifies the multiplication of the assembly, a quantity that correlates with the fissile content. PGET is approved by IAEA (International Atomic Energy Agency) for safeguards measurements, but the feasibility of PNAR has not yet been established. A first of its kind PNAR prototype instrument was built in a collaboration coordinated by STUK. This paper concludes the results of the first measurements of spent BWR (Boiling Water Reactor) nuclear fuel with the prototype in July 2019. Based on the measurements, the ability of the PNAR instrument to detect the presence of fissile material in a repeatable manner in a reasonable amount of time was demonstrated. Furthermore, the instrument was able to detect differences in multiplication between partially and fully spent fuel assemblies, and axial differences in multiplication within a single assembly.Peer reviewe

Characterization of Heavily Irradiated Dielectrics for Pixel Sensors Coupling Insulator Applications

An increase in the radiation levels during the high-luminosity operation of the Large Hadron Collider calls for the development of silicon-based pixel detectors that are used for particle tracking and vertex reconstruction. Unlike the conventionally used conductively coupled (DC-coupled) detectors that are prone to an increment in leakage currents due to radiation, capacitively coupled (AC-coupled) detectors are anticipated to be in operation in future collider experiments suitable for tracking purposes. The implementation of AC-coupling to micro-scale pixel sensor areas enables one to provide an enhanced isolation of radiation-induced leakage currents. The motivation of this study is the development of new generation capacitively coupled (AC-coupled) pixel sensors with coupling insulators having good dielectric strength and radiation hardness simultaneously. The AC-coupling insulator thin films were aluminum oxide (Al2O3) and hafnium oxide (HfO2) grown by the atomic layer deposition (ALD) method. A comparison study was performed based on the dielectric material used in MOS, MOSFET, and AC-coupled pixel prototypes processed on high resistivity p-type Magnetic Czochralski silicon (MCz-Si) substrates. Post-irradiation studies with 10 MeV protons up to a fluence of 10(15) protons/cm(2) suggest HfO2 to be a better candidate as it provides higher sensitivity with negative charge accumulation on irradiation. Furthermore, even though the nature of the dielectric does not affect the electric field within the AC-coupled pixel sensor, samples with HfO2 are comparatively less susceptible to undergo an early breakdown due to irradiation. Edge-transient current technique (e-TCT) measurements show a prominent double-junction effect as expected in heavily irradiated p-type detectors, in accordance with the simulation studies.Peer reviewe

Multispectral photon-counting for medical imaging and beam characterization - A project review

Central focus of the MPMIB project – funded via the Academy of Finland’s RADDESS 2018–2021 programme – has been research towards a next-generation radiation detection system operating in a photon-counting (PC) multispectral mode: The extraction of energy spectrum per detector pixel data will lead to better efficacy in medical imaging with ionizing radiation. Therefore, it can be an important asset for diagnostic imaging and radiotherapy, enabling better diagnostic outcome with lower radiation dose as well as more versatile characterization of the radiation beam, leading for example to more accurate patient dosimetry. We present our approach of fabricating direct-conversion detectors based on cadmium telluride (CdTe) semiconductor material hybridized with PC mode capable application-specific integrated circuits (ASICs), and will give a review on our achievements, challenges and lessons learned. The CdTe crystals were processed at Micronova, Finland’s national research infrastructure for micro- and nanotechnology, employing techniques such as surface passivation via atomic layer deposition, and flip chip bonding of processed sensors to ASIC. Although CdTe has excellent photon radiation absorption properties, it is a brittle material that can include large concentrations of defects. We will therefore also emphasize our quality assessment of CdTe crystals and processed detectors, and present experimental data obtained with prototype detectors in X-ray and Co-60 beams at a standards laboratoryPeer reviewe

Kaasualtistustestin käyttö elektroniikan ympäristörasitustestauksessa

Tämän työn tarkoituksena on ollut kartoittaa tutkimus- ja testausmenetelmiä, joilla voidaan selvittää ilman saasteiden kuten rikkidioksidin ja typen oksidien vaikutuksia elektroniikkalaitteiden toimintojen luotettavuuteen. On päädytty kaasualtistustestiin, joka tunnetaan nimellä Flowing Mixed Gas-testi (FMG). Testillä voidaan simuloida materiaalien ja kokonaisten laitteiden vikaantumista saastuneissa ympäristöissä. Lukuisten testiä käsittelevien artikkelien perusteella se on todettu parhaiten ympäristösaasteiden vaikutuksia simuloivaksi ja realistisimmaksi ympäristörasitustestiksi. Työssä tarkastellaan ensin elektroniikan luotettavuuteen vaikuttavia ilmiöitä kuten korroosiota, diffuusiota ja migraatiota. Luvuissa on käsitelty ilmiöiden teoriaa ja ilmenemismuotoja. Esitellään myös korroosiolle ja migraatiolle altistavia tekijöitä. Samoin esitellään tavallisimmat elektroniikassa käytettävät metallit ja polymeerit sekä niiden käyttökohteet ja ominaisuudet. Tutustutaan myös esimerkin omaisesti liittimissä ja Flip Chip-rakenteissa esiintyviin kontaminaatioihin. FMG-testin yksityiskohtaisempi tarkastelu osoitti sen soveltuvan erinomaisesti liitinten pinnoitteiden, kapselointi- ja piirilevymateriaalien, johdin-eristerakenteiden sekä kokonaisten elektroniikkalaitteiden tutkimiseen. Testissä testattavat kappaleet altistetaan syövyttäville kaasuille ja korkealle kosteudelle. Testissä käytettävien kaasujen: rikkidioksidin, rikkivedyn, kloorikaasun ja typpidioksidin on katsottu riittävän simuloimaan kaikkien ilmakehässä esiintyvien saasteiden vaikutuksia. Työssä on esitelty myös FMG-testiä käsittelevä IEC 68-2-60-standardi. Esitellään kaasualtistustestin suorittamiseen tarvittava laitteisto ja testin kulku. Lopuksi tutustutaan testin turvallisuusnäkökohtiin. Lisäksi on perehdytty muihin elektroniikan tutkimuksessa käytettyihin testeihin. Esitellään 85/85-testi, HAST-testi (Highly accelerated stress test), suolasumutesti ja lämpöshokkitesti sekä pohditaan testien realistisuutta. Havaitaan, että HAST-testi on yhtä luotettava kuin 85/85-testi, mutta kymmenen kertaa nopeampi. Lopuksi pohditaan, miten FMG-testiä voidaan käyttää elektroniikan luotettavuustutkimuksessa. FMG-testi on hyödyllinen varsinkin Integrated Module Board-teknologiassa (IMB), jossa haudataan passiivikomponentteja ja integroituja piirejä polymeeripohjaisen piirilevyn sisään. Teknologiaa kehitetään Elektroniikan valmistustekniikan laboratoriossa

Pixelated silicon detector for radiation beam profile measurements

A pixelated silicon detector, developed originally for particle physics experiments, was used for a beam profile measurement of a cobalt-60 (Co-60) irradiator in a water phantom. The beam profile was compared to a profile measured with a pinpoint ionization chamber. The differences in the pixel detector and pinpoint chamber relative profiles were within approximately 2% of profile maximum, and after calculating correction factors with Monte Carlo simulations for the pixel detector, the maximum difference was decreased to approximately 1% of profile maximum. The detector's capability to measure pulse-height was used to record an electron pulse-height spectrum in water in the Co-60 beam, and the results agreed well with simulations.Peer reviewe

Development of the CMS detector for the CERN LHC Run 3

International audienceSince the initial data taking of the CERN LHC, the CMS experiment has undergone substantial upgrades and improvements. This paper discusses the CMS detector as it is configured for the third data-taking period of the CERN LHC, Run 3, which started in 2022. The entire silicon pixel tracking detector was replaced. A new powering system for the superconducting solenoid was installed. The electronics of the hadron calorimeter was upgraded. All the muon electronic systems were upgraded, and new muon detector stations were added, including a gas electron multiplier detector. The precision proton spectrometer was upgraded. The dedicated luminosity detectors and the beam loss monitor were refurbished. Substantial improvements to the trigger, data acquisition, software, and computing systems were also implemented, including a new hybrid CPU/GPU farm for the high-level trigger

Development of the CMS detector for the CERN LHC Run 3

Since the initial data taking of the CERN LHC, the CMS experiment has undergone substantial upgrades and improvements. This paper discusses the CMS detector as it is configured for the third data-taking period of the CERN LHC, Run 3, which started in 2022. The entire silicon pixel tracking detector was replaced. A new powering system for the superconducting solenoid was installed. The electronics of the hadron calorimeter was upgraded. All the muon electronic systems were upgraded, and new muon detector stations were added, including a gas electron multiplier detector. The precision proton spectrometer was upgraded. The dedicated luminosity detectors and the beam loss monitor were refurbished. Substantial improvements to the trigger, data acquisition, software, and computing systems were also implemented, including a new hybrid CPU/GPU farm for the high-level trigger.Since the initial data taking of the CERN LHC, the CMS experiment has undergone substantial upgrades and improvements. This paper discusses the CMS detector as it is configured for the third data-taking period of the CERN LHC, Run 3, which started in 2022. The entire silicon pixel tracking detector was replaced. A new powering system for the superconducting solenoid was installed. The electronics of the hadron calorimeter was upgraded. All the muon electronic systems were upgraded, and new muon detector stations were added, including a gas electron multiplier detector. The precision proton spectrometer was upgraded. The dedicated luminosity detectors and the beam loss monitor were refurbished. Substantial improvements to the trigger, data acquisition, software, and computing systems were also implemented, including a new hybrid CPU/GPU farm for the high-level trigger

Development of the CMS detector for the CERN LHC Run 3

International audienceSince the initial data taking of the CERN LHC, the CMS experiment has undergone substantial upgrades and improvements. This paper discusses the CMS detector as it is configured for the third data-taking period of the CERN LHC, Run 3, which started in 2022. The entire silicon pixel tracking detector was replaced. A new powering system for the superconducting solenoid was installed. The electronics of the hadron calorimeter was upgraded. All the muon electronic systems were upgraded, and new muon detector stations were added, including a gas electron multiplier detector. The precision proton spectrometer was upgraded. The dedicated luminosity detectors and the beam loss monitor were refurbished. Substantial improvements to the trigger, data acquisition, software, and computing systems were also implemented, including a new hybrid CPU/GPU farm for the high-level trigger

Development of the CMS detector for the CERN LHC Run 3

International audienceSince the initial data taking of the CERN LHC, the CMS experiment has undergone substantial upgrades and improvements. This paper discusses the CMS detector as it is configured for the third data-taking period of the CERN LHC, Run 3, which started in 2022. The entire silicon pixel tracking detector was replaced. A new powering system for the superconducting solenoid was installed. The electronics of the hadron calorimeter was upgraded. All the muon electronic systems were upgraded, and new muon detector stations were added, including a gas electron multiplier detector. The precision proton spectrometer was upgraded. The dedicated luminosity detectors and the beam loss monitor were refurbished. Substantial improvements to the trigger, data acquisition, software, and computing systems were also implemented, including a new hybrid CPU/GPU farm for the high-level trigger

Development of the CMS detector for the CERN LHC Run 3

Since the initial data taking of the CERN LHC, the CMS experiment has undergone substantial upgrades and improvements. This paper discusses the CMS detector as it is configured for the third data-taking period of the CERN LHC, Run 3, which started in 2022. The entire silicon pixel tracking detector was replaced. A new powering system for the superconducting solenoid was installed. The electronics of the hadron calorimeter was upgraded. All the muon electronic systems were upgraded, and new muon detector stations were added, including a gas electron multiplier detector. The precision proton spectrometer was upgraded. The dedicated luminosity detectors and the beam loss monitor were refurbished. Substantial improvements to the trigger, data acquisition, software, and computing systems were also implemented, including a new hybrid CPU/GPU farm for the high-level trigger