SMILE soft X-ray Imager flight model CCD370 pre-flight device characterisation

Throughout the SMILE mission the satellite will be bombarded by radiation which gradually damages the focal plane devices and degrades their performance. In order to understand the changes of the CCD370s within the soft X-ray Imager, an initial characterisation of the devices has been carried out to give a baseline performance level. Three CCDs have been characterised, the two flight devices and the flight spare. This has been carried out at the Open University in a bespoke cleanroom measurement facility. The results show that there is a cluster of bright pixels in the flight spare which increases in size with temperature. However at the nominal operating temperature (−120 °C) it is within the procurement specifications. Overall, the devices meet the specifications when operating at −120 °C in 6 × 6 binned frame transfer science mode. The serial charge transfer inefficiency degrades with temperature in full frame mode. However any charge losses are recovered when binning/frame transfer is implemented

The CCD instrument background of the SMILE SXI

The ESA and CAS SMILE mission orbit is highly elliptical and will pass through multiple radiation environments. The Soft X-ray Imager (SXI) instrument aboard has a radiation shutter door designed to close when the surrounding radiation flux is high. The shutter door will close when passing below an altitude threshold to protect against trapped particles in the Earth’s Van Allen Belts. Therefore, two radiation environments can be approximated based on the shutter door position: open and closed. The instrument background for the CCDs (Charge-Coupled Devices) that form the focal plane array of the SXI were evaluated for the two environments. Due to the correlation of the space environment with the solar cycle, the solar minima and maxima, the background was also evaluated at these two extremes. The results demonstrated that the highest instrument background will occur during solar minima due to the main contributing source being Galactic Cosmic Rays (GCRs). It was also found that the open background was highest for solar minima and that the closed background was highest during solar maxima. This is due to the radiation shutter door acting as a scattering centre and the changes in the energy flux distribution of the GCRs between the two solar extremes

The SMILE Soft X-ray Imager (SXI) CCD design and development

SMILE, the Solar wind Magnetosphere Ionosphere Link Explorer, is a joint science mission between the European Space Agency and the Chinese Academy of Sciences. The spacecraft will be uniquely equipped to study the interaction between the Earth’s magnetosphere-ionosphere system and the solar wind on a global scale. SMILE’s instruments will explore this science through imaging of the solar wind charge exchange soft X-ray emission from the dayside magnetosheath, simultaneous imaging of the UV northern aurora and in-situ monitoring of the solar wind and magnetosheath plasma and magnetic field conditions. The Soft X-ray Imager (SXI) is the instrument being designed to observe X-ray photons emitted by the solar wind charge exchange process at photon energies between 200 eV and 2000 eV. X-rays will be collected using a focal plane array of two custom-designed CCDs, each consisting of 18 µm square pixels in a 4510 by 4510 array. SMILE will be placed in a highly elliptical polar orbit, passing in and out of the Earth’s radiation belts every 48 hours. Radiation damage accumulated in the CCDs during the mission’s nominal 3-year lifetime will degrade their performance (such as through decreases in charge transfer efficiency), negatively impacting the instrument’s ability to detect low energy X-rays incident on the regions of the CCD image area furthest from the detector outputs. The design of the SMILE-SXI CCDs is presented here, including features and operating methods for mitigating the effects of radiation damage and expected end of life CCD performance. Measurements with a PLATO device that has not been designed for soft X-ray signal levels indicate a temperature-dependent transfer efficiency performance varying between 5 × 10−5 and 9 × 10−4 at expected End of Life for 5.9 keV photons, giving an initial set of measurements from which to extrapolate the performance of the SXI CCDs

Effects of temperature anneal cycling on a cryogenically proton irradiated CCD

Throughout a typical Earth orbit a satellite is constantly bombarded by radiation with trapped and solar protons being of particular concern as they gradually damage the focal plane devices throughout the mission and degrade their performance. To understand the impact the damage has on CCDs and how it varies with their thermal history a proton radiation campaign has been carried out using a CCD280. The CCD is irradiated at 153 K and gradually warmed to 188 K in 5 K increments with Fe55 X-ray, dark current and trap pumping images taken at 153 K after each anneal step. The results show that despite the trap landscape changing throughout the anneal it has little impact on parallel charge transfer inefficiency. This is thought to be because most traps are unaffected and a lot of those that do anneal only move from the continuum between distinct trap species and into a nearby divacancy trap “peak” whose emission time constant is similar enough to still impact the CTI. In terms of using a CCD280 or similar devices in a mission the CTI being unaffected by thermal annealing up to 188 K means that any CTI correction needed as the radiation damage builds up does not have to take into account the thermal history of the focal plane. However, it is possible that a significant amount of annealing will occur at temperatures greater than 188 K and care should be taken when a mission is operating in this range to gather accurate pre-flight data

Developing the active trap model for CCD charge transfer optimisation in large-scale space missions

Charge coupled devices (CCDs) have been the detector of choice for large-scale space mission for many years. Although dominant in this field, the charge transfer performance of the technology degrades over time due to the harsh space-radiation environment. Charge transfer performance can be optimized however, but it is often time consuming and expensive due to the many operating modes of the CCDs. A new technique is presented and developed here, which uses new measurements of the trap landscape present in a CCD, to predict changes in charge transfer inefficiency as a function of different variables. By using this technique, it is possible to focus experimental lab testing on key device parameters, potentially saving many months of laboratory effort. Due to the generality of the method, it can be used to optimize the charge transfer performance of any CCD, and as such has many uses across a wide range of fields. Future CCDs variants that will be used in potential space missions (EMCCD and p-channel CCDs) can use this technique to feedback key device performance to the wider mission consortium before devices are available for experimental testing

History, Commemoration, and Belief: Abraham Lincoln in American Memory, 1945-2001

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91765/1/Schuman-History_Commemoration_Belief.pd

Evidence-based Kernels: Fundamental Units of Behavioral Influence

This paper describes evidence-based kernels, fundamental units of behavioral influence that appear to underlie effective prevention and treatment for children, adults, and families. A kernel is a behavior–influence procedure shown through experimental analysis to affect a specific behavior and that is indivisible in the sense that removing any of its components would render it inert. Existing evidence shows that a variety of kernels can influence behavior in context, and some evidence suggests that frequent use or sufficient use of some kernels may produce longer lasting behavioral shifts. The analysis of kernels could contribute to an empirically based theory of behavioral influence, augment existing prevention or treatment efforts, facilitate the dissemination of effective prevention and treatment practices, clarify the active ingredients in existing interventions, and contribute to efficiently developing interventions that are more effective. Kernels involve one or more of the following mechanisms of behavior influence: reinforcement, altering antecedents, changing verbal relational responding, or changing physiological states directly. The paper describes 52 of these kernels, and details practical, theoretical, and research implications, including calling for a national database of kernels that influence human behavior

The Soft X-ray Imager (SXI) on the SMILE Mission

The Soft X-ray Imager (SXI) is part of the scientific payload of the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission. SMILE is a joint science mission between the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS) and is due for launch in 2025. SXI is a compact X-ray telescope with a wide field-of-view (FOV) capable of encompassing large portions of Earth’s magnetosphere from the vantage point of the SMILE orbit. SXI is sensitive to the soft X-rays produced by the Solar Wind Charge eXchange (SWCX) process produced when heavy ions of solar wind origin interact with neutral particles in Earth’s exosphere. SWCX provides a mechanism for boundary detection within the magnetosphere, such as the position of Earth’s magnetopause, because the solar wind heavy ions have a very low density in regions of closed magnetic field lines. The sensitivity of the SXI is such that it can potentially track movements of the magnetopause on timescales of a few minutes and the orbit of SMILE will enable such movements to be tracked for segments lasting many hours. SXI is led by the University of Leicester in the United Kingdom (UK) with collaborating organisations on hardware, software and science support within the UK, Europe, China and the United States

The Soft X-ray Imager (SXI) on the SMILE Mission

The Soft X-ray Imager (SXI) is part of the scientific payload of the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission. SMILE is a joint science mission between the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS) and is due for launch in 2025. SXI is a compact X-ray telescope with a wide field-of-view (FOV) capable of encompassing large portions of Earth’s magnetosphere from the vantage point of the SMILE orbit. SXI is sensitive to the soft X-rays produced by the Solar Wind Charge eXchange (SWCX) process produced when heavy ions of solar wind origin interact with neutral particles in Earth’s exosphere. SWCX provides a mechanism for boundary detection within the magnetosphere, such as the position of Earth’s magnetopause, because the solar wind heavy ions have a very low density in regions of closed magnetic field lines. The sensitivity of the SXI is such that it can potentially track movements of the magnetopause on timescales of a few minutes and the orbit of SMILE will enable such movements to be tracked for segments lasting many hours. SXI is led by the University of Leicester in the United Kingdom (UK) with collaborating organisations on hardware, software and science support within the UK, Europe, China and the United States

Experimental Study of the NIEL Scaling for Silicon Devices

This paper proposes some new experimental data comparing the damage factor of silicon devices with the NIEL after electron, proton and gamma irradiations. The results show that the measured damage factors fit better with the “effective” NIEL, an alternative model of displacement damage effects, than with the classical one