January 6, 2020: FOXSI's X-ray Optics and Detectors Put the Sun in Focus
September 4, 2018: NASA-funded Rocket to View Sun with X-Ray Vision
November 14, 2017: Proposed NASA Mission Would Investigate Where Space Weather Begins
July 27, 2017: NASA Selects Proposals to Study Sun, Space Environment
December 12, 2014: NASA-funded FOXSI to observe x-rays from the Sun
November 2, 2012: A Next-Generation X-Ray Telescope Launches
Berkeley Science Review
Novermber 9, 2012: FOXSI Fires Up
Other FOXSI-related Stories
October 10, 2017: FOXSI may reveal why Sun’s corona is so hot
October 10, 2017: New theory on why the sun's corona is hotter than its surface
October 9, 2017: Tiny Explosions May Power the Sun's Blazing Corona
December 8, 2014: FOXSI to observe X-rays from Sun
Global FOXSI Stories
October 22, 2017: Foxsi: el experimento de la Nasa que convierte un arma en ciencia
October 11, 2017: Нова гіпотеза пояснює, чому корона Сонця більш гаряча, ніж його поверхня
October 10, 2017: Explicación a por qué la corona solar es más caliente que el interior
October 10, 2017: 「見えない」ナノフレア、太陽X線超高感度観測で発見した存在の証拠
October 12, 2017: Perché la corona solare è così calda?
October 10, 2017: Разогрев солнечной короны объяснили «нановспышками»
October 12, 2017: Ученые: Причина колоссальной температуры короны Солнца разгадана
March 22, 2018: UMN Detector Testing
At the beginning of February, our teammates Lindsay and Julie traveled to Sagamihara, Japan to receive the new CdTe detectors from our teammates at the Institute for Space and Astronautical Science (ISAS). With the new detectors safely arrived in Minnesota, our testing and calibration in the lab has begun. Julie, Athiray, Sophie, Kento, Ishikawa san, Lance, Connor, and Lindsay have been working as a group to calibrate the detectors in time for our scheduled delivery to Berkeley at the end of April.
Julie has been working specifically to understand the noise characteristics of our spare FOXSI-3 detector and claims “we've already seen beautiful spectra from Am-241 and Fe-55,” which are two of our radioactive sources. She is also updating the CdTe calibration code to better understand detected photons and developing a new single-detector cooling system. This more compact system will make for easier transport when we travel to the Advanced Light Source at Lawrence Berkeley National Laboratory to further measure detector efficiency.
Athiray explains that one of our primary testing goals is to produce noise check results that are consistent with the ISAS measurements. He and the others have been able to accomplish this objective by studying noise characteristics under different conditions and ultimately mitigating trigger noise.
Meanwhile, Sophie has been working with Ishikawa to test a prototype of the soft X-ray detector, PHOENIX. Initially, mechanical tests elucidated difficulties in fitting the prototype into the detector housing of the focal plane due to the number of wires hooked up to the detector; however, it ultimately fit with minor adjustments. Upon further testing, communications between the Phoenix detector and the formatter board appear successful. We have also been testing the new CdTe detectors in the focal plane with the PHOENIX detector in controlled cooling conditions.
As we continue to discuss our initial experimental results, we are planning for our next course of action, which includes a plan to integrate and test the detectors upon delivery to Berkeley
January 4, 2018: AGU Fall Meeting Presentations
At the 2017 AGU Fall Meeting in New Orleans, our FOXSI rocket team members, Lindsay, Athiray, Julie, and Steven, as well as Albert Shih of the FOXSI Small Explorer (SMEX) team represented our projects via posters and oral presentations. Julie and Athiray presented about the results obtained from two microflares observed by FOXSI-2 on December 11, 2014. Meanwhile, Lindsay gave a comprehensive talk recounting what we know about small flares based on FOXSI and NuSTAR’s results to date. She, Steven, and Albert additionally presented on details regarding the FOXSI SMEX Phase A concept study. Read on for more detailed descriptions of each presentation.
Athiray presented on data collected from FOXSI’s second flight, in which we observed significant hard X-ray emissions during the two solar microflares. As he detailed in his presentation, “some of these flares [heated] up to several million Kelvin and were visible in the Extreme Ultraviolet (EUV) with Atmospheric Imaging Assembly (AIA).” By combining FOXSI-2 data with data from the Solar Dynamics Observatory’s AIA, and the Hinode X-ray Telescope, he explained that we were able to better constrain the differential emission measure (DEM) than is possible with isolated observations. Constraining the DEM is crucial in understanding energy release in solar corona.
Julie also presented about results obtained from FOXSI-2 observations, focusing on spectral analysis of FOXSI-2’s first microflare. She explained in her presentation that our sensitive instrumentation has the capability to perform spectral analyses of microflares significantly fainter than any observed by FOXSI’s predecessor, RHESSI. As evidenced by our imaging spectroscopy, the first FOXSI-2 microflare appears to have released complex energy releases, indicating that these small flares are still made up of numerous even smaller events. Furthermore, Julie described how the two new CdTe detectors flown with FOXSI-2 offer improved efficiency compared to our Si detectors while maintaining the spectral capabilities exhibited by our Si detectors.
Lindsay centered her oral presentation on the latest results relating to small flares obtained from both FOXSI and NuSTAR. She explained that, thus far, measurements derived from small flares appear consistent with the standard flare model. While NuSTAR has observed that small flares occur even within the quiet regions of the Sun, analysis of FOXSI-2 data alludes to the possibility of even smaller nanoflares. Concurrently, in her poster presentation, Lindsay detailed the FOXSI SMEX Phase A concept study and its prospects for studying coronal jets and accelerated electrons.
Steven also spoke about the FOXSI SMEX mission and its potential to bring a “new perspective on energy release and particle acceleration on the Sun.” He explained that this version of FOXSI is a direct imaging X-ray spectrometer with higher dynamic range and more than ten times the sensitivity of existing instruments. The FOXSI SMEX mission will employ instruments similar to those of the FOXSI sounding rocket such as focusing optics and pixelated solid-state detectors to directly image solar hard X-rays for the first time. With this state-of-the-art instrumentation, FOXSI SMEX will be sensitive enough to observe both large and small flares, as well as escaping electrons and hot active regions of the Sun.
March 31, 2017: Collimator Prototype
On March 1, two of our team members, Shin-nosuke Ishikawa of JAXA/ISAS and Noriyuki Narukage of NAOJ, viewed a 3D-printed prototype of a collimator we will be using for FOXSI-3. Our collimators are cylindrical structures that filter photons by directing them through thousands of minute channels. This technology will be secured to two of our optics modules to prevent photons traveling from unwanted angles (i.e., ghost rays) from hitting our detectors, which is important because it will allow us to gather more accurate data from the particular regions of the sun we are interested in.
The particular 3D-printed model pictured here is designed for one of our optics modules with a special detector calibrated for soft x-rays. While this collimator could also be used to aid hard x-ray detection, we are exploring other models that use different fabrication methods to potentially maximize the number of channels. Currently, we are considering a model consisting of bundled optical fibers, which provides many more channels with considerably smaller diameters. The advantage of this model is its relative height. While the 3D-printed model stands about nine inches tall, the fiber-optic model is a mere two inches due to the compactness of its channels. Essentially, the shorter the collimator is, the easier it is to install. By implementing two different models, we will also be able to compare and learn from their results.
On March 17, our team members at UC Berkeley were also able to view the 3D-printed prototype.
October 18, 2017: Optics Calibration at NMSFC
In the beginning of October, our team members Milo, Athiray, Sasha, Brian, Patrick, and Lindsay convened at the NASA Marshall Space Flight Center for a highly successful week of optics calibration in the Stray Light Facility (SLF). Our team members were able to follow Milo's detailed calibration plan and complete tests measuring the half-power diameter, point spread function, and effective area for three of our seven modules—X4, X2, and X0. By testing three different modules, we were able to collect data for both our 7-shell (X4) and 10-shell (X2, X0) modules types. Our teammates used both a CdTe detector and an SDD detector in tandem with the modules throughout the testing process. After the first few days of tests with the CdTe detector, our team opted to switch to the already calibrated SDD detector to complete the remaining tests smoothly.
Since the cumulative 62 hours of valuable work completed in the SLF, our teammates have traveled back to their respective homes. Milo has been working hard to generate preliminary analyses of the tests to present for our upcoming design review at the end of this week (10/19–10/20) at the University of Minnesota.
September 5, 2017: SPIE Presentations
At the 2017 Optics + Photonics SPIE conference in San Diego, several of our FOXSI team members presented compelling work related to the progress of our instrumentation.
On the first day of the conference, one of our postdoctoral researchers, Subramania Athiray, gave a presentation entitled “Calibration of the hard X-ray detectors for the FOXSI solar sounding rocket.” In this paper, he offers significant methodological improvements for our Si detector calibration design. Overall, Athiray’s work will help us better calibrate the Si detectors for our upcoming flight and more effectively analyze data from past flights. This strong foundation will also allow us to improve the calibration methods of our CdTe detectors in the future.
Noriyuki Narukage san, our colleague at the National Astronomical Observatory of Japan, also presented at SPIE. His paper and presentation, titled “Photon counting type imaging spectrometer for solar soft x-rays,” focuses on how we plan to observe plasma in the solar corona during our third launch with a high-speed soft X-ray camera. The powerful back-illuminated CMOS sensor used in this design will allow the camera to capture more light with a continuous exposure for 1k x 100 pixels. Narukage-san’s work gives us technology that can generate soft X-ray spectra with enough precision for the solar activity we will be observing and will be paired with a traditional FOXSI optics module for the third flight.
Later in the conference, one of our graduate student researchers, Milo Buitrago-Casas, presented the content of his paper, titled “Methods for reducing singly reflected rays on the Wolter-I focusing mirrors of the FOXSI rocket experiment.” Here he delineates the various structures we have considered to help reduce the impact of singly reflected rays (i.e., photons that do not focus properly) on our optics modules: cylindrical baffles, two types of honeycomb collimators, and wedge absorbers. Following Milo’s in-depth analysis of these technologies in relation to FOXSI’s goals, he explains our decision to include one of each type of honeycomb collimator in our FOXSI-3 flight setup, as well as a wedge absorber. His valuable research will ultimately help us reduce the negative impact of singly reflected rays on the sensitivity of our instruments.
Dan Ryan also presented about the progress of new detector technology called HEXITEC, or High Energy X-ray Imaging Technology. His paper entitled “Modeling and measuring charge sharing in hard x-ray imagers using HEXITEC CdTe detectors,” describes the development of fine-pixelated spectral X-ray detectors that we will be using for the FOXSI SMEX. The design features that make HEXITEC especially useful for FOXSI’s observations are its high readout rate (increasing the upper limit of the manageable count rate and reducing the need for attenuation), as well as its small pixel size (allowing it to over-sample the point spread function of current hard X-ray focusing optics). However, small pixels also promote charge sharing—a phenomenon that, can degrade energy resolution if not accounted for, but can also enable higher spatial resolution. As result, models of charge sharing, like the one outlined by Dan Ryan, must be developed and tested before the full potential of HEXITEC can be exploited in new missions like FOXSI.
All of our team members’ presentations were well-received by their SPIE audiences, and we are very proud of them! New detectors, calibration techniques, and optical components can be useful for projects beyond FOXSI that study the solar corona or other regions of the Sun because many rockets and spacecraft employ similar instruments. Thus, their work is significant not only to the progress of our team but also to the field of solar physics research in general.
All of these contributions are published as papers in the proceedings from this conference and can be accessed in the SPIE Digital Library under the sections entitled Solid State Detectors I and X-Ray Telescopes.
July 31, 2017: SMEX Phase A
On July 28, 2017, NASA formally announced that FOXSI is one of nine selected proposals under the Explorers Program that will study the Sun and space environment. Each of the proposals was chosen based on their scientific potential and feasibility. The five Heliophysics Small Explorer (SMEX) projects will each receive $1.25 million to conduct an 11-month “mission concept study” called Phase A. Once the 11-month study is completed, NASA will then select one or more SMEXes to move on to Phase B and beyond with the hope of fabricating and launching the spacecraft.
This accomplishment is monumental for our team, and we would like to especially thank our teammate Steven Christe of NASA/Goddard for leading our successful Phase A proposal. We are very excited about this new opportunity to demonstrate what FOXSI can do for science! To read the full article published by NASA, click here.
June 15, 2017: Detector Testing
Last month, we hosted our team from Japan, as well as our project manager from the University of California Berkeley, at the University of Minnesota so that we could test the capabilities of one of our new Cadmium Telluride (CdTe) detectors. Our colleagues in Japan first developed CdTe detectors for FOXSI-2 and have since been making improvements to optimize their use for collecting data on hard X-rays from the Sun—the primary interest of our study. As a result, we now have the finest-resolution CdTe strip detectors ever made.
During the testing process, both the new detector as well as one of the CdTe detectors that flew with FOXSI-2 were used to compare their performance (test setup pictured left). We manipulated several variables such as bias voltage, integration time, format, source, and temperature for each trial to determine the CdTe detector’s optimal settings for sensitivity. Overall, our week of testing yielded two valuable outcomes: (1) we confirmed that our new detector successfully interfaces with the flight setup we will be using at launch in August 2018; and (2) we collected calibration data that can help us analyze and improve our setup.
We also discussed positive results obtained at the University of Minnesota regarding new ways of taking calibration data for the Si detectors. By using fluorescence of Copper and Nickle foils in addition to radioactive sources (e.g., Fe-55, Am-241, Ba-133), we can improve our gain calibration