The Special Issue of NIMA for ULITIMA 2018

Zhehui Wang, Marcel Demarteau, John Kline

Research output: Contribution to journalEditorial

Funding

Zhehui Wang Los Alamos National Laboratory, Los Alamos, NM 87545, USA Los Alamos National Laboratory Los Alamos NM 87545 USA Los Alamos National Laboratory, Los Alamos, NM 87545, USA Marcel Demarteau Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA Oak Ridge National Laboratory Oak Ridge TN 37830 USA Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA John Kline Los Alamos National Laboratory, Los Alamos, NM 87545, USA Los Alamos National Laboratory Los Alamos NM 87545 USA Los Alamos National Laboratory, Los Alamos, NM 87545, USA There are a number of international workshops and conferences dedicated to imaging sensors, particle tracking instrumentation and related developments. They include but are not limited to the International Congress on High-Speed Imaging and Photonics (ICHSIP, biannual), the International Workshop on Radiation Imaging Detectors (iWoRID, annual), International workshop on Semiconductor pixel detectors for particles and imaging (PIXEL, triennial), the International Image Sensor Workshop (IISW, triennial) by the International Imaging Sensor Society, the annual CPAD Instrumentation frontier workshop that addresses new technologies for particle and nuclear physics discovery, and the National Diagnostics Working Group workshop sponsored by the NNSA of the US Department of Energy. So why UL trafast I maging T racking I nstrumentation, M ethods and A pplications (ULITIMA), which was held at the Argonne National Laboratory (Lemont, IL, USA) in September, 2018? Some detailed rationales are given below. Short answer is that the science-and-technology-driven themes of ULITIMA are sufficiently balanced and distinct that it can promote stimulating exchange of ideas and synergies among different disciplines. ULITIMA 2018 is the sequel to one of the earlier MaRIE workshops, Ultrafast and High-Energy X-ray Imaging Technologies & Applications, held in Santa Fe, NM, USA in August, 2016. MaRIE (Matter-Radiation Interactions in Extremes) was proposed as a future flagship facility by Los Alamos National Laboratory to design and tailor ‘controlled functions’ of a material for the unique demands of particular applications. MaRIE experiments were envisioned not only to validate material designs, properties, and functions, but also to develop and certify new material processing technologies such as additive manufacturing in-situ. Specifically, by using an X-ray Free Electron Laser (XFEL) with a first harmonic energy at up to 42 keV, MaRIE would generate experimental material data that would bridge the mesoscopic gap among the existing NNSA facilities such as DARHT, U1a (both of which can produce macroscopic dynamic data), NIF and Z (both of which can produce nanoscopic dynamic data). It was clear to the participants of the August 2016 Santa Fe workshop that, collecting the MaRIE XFEL data would present instrumentation challenges of its own, and there was no off-the-shelf solution at the time. A ‘MaRIE camera’ needs to efficiently collect mega-pixel (order of one million pixels) multi-frame images at about one billion frames per second generated by high-energy X-ray scattered from mesoscopic scenes. Although technological pieces exist that can partially satisfy some aspects of the performance requirements, they have yet to be combined in an integrated system, i.e ., a MaRIE camera, to simultaneously achieve GHz frame-rate, multiple frames of images, high detection efficiency for high energy X-rays, sufficient spatial or pixel resolution, and with a mega-pixel format. As summarized in the Los Alamos report (LANL report number LA-UR-17-22085) for the 2016 workshop, it appears to be logical and necessary, guided by previous experiences from other synchrotron and XFEL imaging cameras, to separate such development into two phases, with phase I aiming at 100 MHz or higher frame rates for efficient imaging using 20 keV or higher energy X-rays, and phase II at one GHz and higher frame-rates with similar or better performance otherwise. Interest in 100 MHz and higher frame-rate imaging goes far beyond the need of the MaRIE facility. Ultrafast phenomena are commonplace on the mesoscopic ( ∼ micrometers) and smaller length scales. To resolve the motion of a one micrometer object moving at 1 km/s, it requires a temporal resolution around 1 ns. To resolve the motion of an electron in a molecule, it requires femtosecond photography techniques, as pioneered by A. Zewail and colleagues. ‘Freezing’ the ultrafast motion through ultrafast imaging is regarded as the essential step towards unwrapping the mysteries associated with ultrafast processes from chemical reactions, to molecular interactions during cellular function, and to phase transitions under shock loading. The keynote talk by Marius Schmidt (University of Wisconsin, Milwaukee, USA) highlighted the recent results in Serial Femtosecond Crystallography using XFELs. The successes of the serial femtosecond crystallography and other pump–probe experiments illustrate that, once again, the femtosecond X-ray source from an XFEL can significantly relax the requirements on the detector performance including temporal responses. In other words, it is possible to capture ‘fast images’ by a ‘slow camera’. Some related work in adopting ultrafast pulses for ultrafast imaging in the optical regime was reported by Keiichi Nakagawa (University of Tokyo) and collaborators, by Mark Foster’s group (Johns Hopkins University), and by Jinyang Liang (INRS, Canada) and collaborators. The steady increase of high-speed imaging camera framerates, which started since the invention of photographic films, has continued in the digital imaging era, in which CCD cameras since 1980s and CMOS cameras more recently have now taken over. The keynote talk by one of the CMOS imaging sensor pioneers, Eric Fossum (Dartmouth), sheds light upon the history and some near-term possibilities. There is no reason to believe that the push for even higher frame-rate and other improved performance will abate. The talk given by Takeharu Goji Etoh (Ritsumeiken University, Japan) gave a theoretical temporal resolution estimate for silicon-based sensor to be about 11 ps, and included a roadmap for high-speed imaging hardware. Besides impact on cameras with silicon and other semiconductor sensors, CMOS ASICs are now also injecting fresh blood to other traditional high-speed imaging methods that use photocathodes, ultrafast gating for electrons, light intensifiers such as micro-channel plate (MCP) technologies. By precisely timing the visible photons, multiple groups have recently reported femtosecond photography, which is related to but distinct from femtochemistry using precisely timed electrons. The combination of traditional MCP techniques or non-vacuum based light intensifiers with new pixelated ASIC chips is reported in the talks of Anton Tremsin (UC Berkeley) and Andrei Nomeroski (Brookhaven National laboratory). Both techniques use the Timepix3 chip developed by CERN. Since the Timepix3 chip does not have in-pixel memory, this and other similar cameras are particularly suited for low-light intensity imaging with low photon occupancy in the full camera. The Sandia Ultrafast X-ray Imaging (UXI) team, represented by Liam Claus and Gideon Robertson, adopted the in-pixel memory approach in their ROIC chips and reported imaging capabilities with a few ns temporal resolution for a few ultrafast frames. The Sandia UXI chip series is now and will continue to be the core technology for the US ICF program, as summarized by the keynote talk of Michael Campbell (University of Rochester). However, it may require further innovations for efficient imaging cameras at X-ray energies above 20 keV due to the lack of, for example, X-ray focusing optics, X-ray mirrors, X-ray beam splitters, and efficient photocathodes for X-rays. One approach is to pursue high quantum efficiency (QE) pixelated photocathodes (presented by Harry Van der Graaf, Nikhef and TU Delft). Paradoxical as it may seem, GHz and higher frame-rate X-ray imaging cameras may need new materials or structures that are yet to be discovered or implemented through ultrafast imaging enabled research in the synchrotron and/or XFEL facilities. Other candidate materials or material structures such as flat optics, photonic crystals, and quantum dots have been studied extensively but not for ultrafast X-ray imaging or particle tracking applications. In short, material and structure challenge are fundamental to the ultrafast imaging and particle tracking. As the push for higher framerates continues, the material limits such as the electron drift time, recombination time in silicon, scintillator decay times, now become important design and fabrication factors. Similar to the 2016 Santa Fe workshop, ULITIMA 2018 included high-speed X-ray imaging instrumentation as a central theme. The talks given by Hugh Philipp (Cornell University), Ulrich Trunk (DESY) summarized the state-of-the-art in high-speed X-ray imaging with emphasis on X-ray synchrotron and XFEL applications. The talk by Tom Zimmerman (Fermilab) described the FASPAX camera design to deliver 10 Mfps in burst mode. Other 10 MHz or faster devices and prototypes were reported by Farah Fahim (Fermilab) on FCP130, and Jose Repond (Argonne National Laboratory) on ultrafast silicon detectors. It was recognized in 2016 that 100 MHz framerate high-energy X-ray burst mode camera may be feasible by pushing the limits of current designs and employing smaller CMOS features than previous imaging cameras such as CS-PAD for LCLS (TSMC 0.25 um), AGPID for European XFEL (Global Foundry 130 nm); Indeed, a 100 MHz burst mode visible camera prototype with a global shutter has since been reported by Rihito Kuroda and collaborator from the Tohoku University, Japan. A new opportunity for X-ray imaging would be to combine the new camera prototypes with fast scintillators to demonstrate 100 MHz burst mode X-ray imaging. Existing approaches for 10 MHz X-ray imaging with hundreds or more frames are now routinely used in existing synchrotron X-ray experiments, as highlighted in the talks by Kamel Fezzaa (Argonne National Laboratory), Tao Sun (Argonne National Laboratory), Wayne Chen (Purdue University), Todd Hufnagel (Johns Hopkins University) and collaborators using the APS 32-ID beam line at Argonne National Laboratory. Progress and results on dynamic X-ray imaging were also reported by Tiqiao Xiao (Shanghai Institute of Applied Physics) and collaborators using the Shanghai Synchrotron Radiation Facility (SSRF). However, since some of the brightest scintillators such as LYSO:Ce, a Cerium doped Lutetium based scintillation crystal, have a characteristic decay time around 40 ns, the indirect method that combines a scintillator X-ray convertor with a 10 ns or fast optical camera may now be limited by the scintillator decay time. It is known that the light yield of many scintillators can be increased significantly at cryogenic temperatures; however, using a cryo-cooled ultrafast X-ray camera is not currently common practice. Continuous research to discover a new generation of fast scintillators with characteristic decay time of 10 ns or less at room temperature, or achieving better light collection efficiency from the known fast scintillators are possible near-term options. Metamaterial for visible light offers new possibilities, as discussed in Paul Lecoq’s keynote talk for 10-ps or less timing and positron emission tomography (PET) applications. A new result to suppress the long-decay-component in BaF 2 through Yttrium was reported by Renyuan Zhu (Caltech) and collaborators. However, the doping scheme did not yet lead to any increase in the light output from the sub-ns decay component. The ULITIMA presentations also showed that besides imaging, additional motivations for sub-ns temporal resolution come from precision timing applications. The talks by Adriano Lai (INFN, Italy) and collaborators, Ron Lipton (Fermilab) and collaborators, and others motivated the particle tracking applications in high-energy physics driven by hadron colliders. In the spirit of synergy and complementarity to other conferences on high-speed imaging, ULITIMA 2018 attempted to broaden the scope of the 2016 workshop in three additional thrusts: tracking, methods and applications. In addition to optical high-speed imaging as mentioned above, ultrafast particle tracking, which is closely related to ultrafast imaging, is now also included. Historically, investments by CERN in various research areas and ASIC’s have seen wide impact including work presented in ULITIMA2018. Examples included RD50 for radiation hard semiconductor devices for very high luminosity colliders, Medipix collaborations, RD42 for radiation hard diamond sensors, and more recently silicon detectors capable of particle tracking with 40 MHz. Will the advances in both fields drive similar development and more close collaborations? Pixelated diamond detectors are already in use as beam monitors in synchrotrons (John Smedley and collaborators, Brookhaven National Laboratory). In addition to ‘detector grade’ materials, cost and yield issues associated with fabrication certainly play a role. Further pushes to GHz framerate through feature size reduction at the foundry motivates synergies from applications in different fields. Multi-wafer runs are commonly used partially due to non-technical reasons such as high cost and low yield associated with the use of the state-of-the-art processes offered by TSMC and other foundries. Emerging 3D integration fabrication offers new possibilities in terms of device designs, but such new technologies are yet to be adopted widely, especially for high-speed pixelated sensor and electronics. 3D trenched-electrode sensors are highlighted by Gian-Franco Della Betta (University of Trento/INFN, Italy) and collaborators. Exploration of synergies with applications other than fast imaging camera development, such as ultrafast particle tracking applications in high-energy physics, would be mutually beneficial. In the context of high-energy physics such as the high-luminosity large hadron collider (LHC), the need for high-tracking rate is driven by the event rate during hadron collisions. One direction of development is to continue to push the performance limits of mono-lithic active pixelated sensors (MAPS). The topic was covered by the talks of Gabriella Carini (Brookhaven National Laboratory), Walter Snoeys (CERN), Leo Greiner (Lawrence Berkeley National Lab) and collaborators. Another type of synergy was revealed between electronics and photonics in the keynote talk by Federico Capasso (Harvard). Flat optics can potentially revolutionize photon-detectors in many different ways, including sharing the same fabrication platform predominantly devoted to electronics. Since Richard Feynman’s 1959 talk ‘There’s Plenty of Room at the Bottom,’ the silicon used in semiconductors now operates at or near intrinsic material limits. It may be surprising to see that the technology advances driven by Moore’s law for transistors and electronics can be extended to make ‘highways’ for photons, with visible and infrared photon applications in sight. ULITIMA 2018 happened at an interesting time. Traditional hardware-centric approaches may no longer provide the optimal solutions in view of big data and information theory, and more recently quantum information science and technology. For example, essentially all the detectors for photons and neutrons in use are ‘destructive’ in the sense that photons and neutrons are only ‘detected’ once due to absorption and no longer available for detection for a second time. Quantum science invites new thinking about non-destructive detection methods, or ‘quantum non-demolition’ schemes. An example of quantum annealing was highlighted by the keynote speech of Maria Spiropulu (Caltech). The talks by Girish Agarwal (Texas A & M University), Jou-Mei Chu (Purdue University), David Fittinghoff (Lawrence Livermore National Laboratory), Paul Fuoss (SLAC National Accelerator Laboratory), Olga Kocharovskaya (Texas A&M University), Shensheng Han (Shanghai Institute of Optics and Fine Mechanics), Isar Mostafanezhad (Nalu Scientific), Angelo Rivetti (INFN), Richard Sandberg (Los Alamos National Laboratory), Tom Smith (the Yanhua Shih group, University of Maryland, Baltimore County), James Sturm (Princeton University), Christine Sweeney (Los Alamos National Laboratory), Stephen Watts (University of Manchester), Sebastian White (CERN, also with University of Virginia), Mei Yuan (Brookhaven National Laboratory), and others presented recent results, new possibilities and challenges associated with data handling, data techniques such as machine learning, quantum principles to enhance visible, X-ray imaging and detection. This special issue co-locates around 20 peer-reviewed papers, some of which were presented as posters. Other materials from the workshop, including most of the oral presentations, are archived and openly accessible from https://indico.fnal.gov/event/ANLHEP1390/ or the mirror site https://www.lanl.gov/conferences/ulitima/index.php . We also would like to thank many people who submitted the images for the best image award (sponsored by Sichuan Tianle Photonics Co.), and congratulate Niranjan Parab of Argonne National Laboratory as the winner. We would like to thank many people who have made the workshop and the special issue possible: The scientific committee members (the list can be found here, https://indico.fnal.gov/event/ANLHEP1390/page/7 ), organizers and coordinators including Samantha Tezak (Argonne National Laboratory), Arianna Gleason (SLAC National Accelerator Laboratory), Petra Merkel (Fermilab), Xuan Li (Los Alamos National Laboratory), Cinzia Da Via (University of Manchester), Marcos Sanchez (Sandia National Lab), Carlo Segre (Illinois Institute of Technology), Rich Sheffield (Los Alamos National Laboratory), Cris Barnes (Los Alamos National Laboratory), Lucy Maestas (Los Alamos National Laboratory), Bob Wagner (Argonne National Laboratory), Gregory Deptuch (Fermilab), and the NIMA editors Viviana Letizia, David Wehe (University of Michigan), Elsevier editorial office staff, and many anonymous reviewers for timely reviews of the papers. Thank you!

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