Hammerhead, an ultrahigh resolution ePix camera for wavelength-dispersive spectrometers

Wavelength-dispersive spectrometers (WDS) are often used in synchrotron and FEL applications where high energy resolution (in the order of eV) is important. Increasing WDS energy resolution requires increasing spatial resolution of the detectors in the dispersion direction. The common approaches with strip detectors or small pixel detectors are not ideal. We present a novel approach, with a sensor using rectangular pixels with a high aspect ratio (between strips and pixels, further called "strixels"), and strixel redistribution to match the square pixel arrays of typical ASICs while avoiding the considerable effort of redesigning ASICs. This results in a sensor area of 17.4 mm x 77 mm, with a fine pitch of 25 $\mu$m in the horizontal direction resulting in 3072 columns and 176 rows. The sensors use ePix100 readout ASICs, leveraging their low noise (43 e$^-$, or 180 eV rms). We present results obtained with a Hammerhead ePix100 camera, showing that the small pitch (25 $\mu$m) in the dispersion direction maximizes performance for both high and low photon occupancies, resulting in optimal WDS energy resolution. The low noise level at high photon occupancy allows precise photon counting, while at low occupancy, both the energy and the subpixel position can be reconstructed for every photon, allowing an ultrahigh resolution (in the order of 1 $\mu$m) in the dispersion direction and rejection of scattered beam and harmonics. Using strixel sensors with redistribution and flip-chip bonding to standard ePix readout ASICs results in ultrahigh position resolution ($\sim$1 $\mu$m) and low noise in WDS applications, leveraging the advantages of hybrid pixel detectors (high production yield, good availability, relatively inexpensive) while minimizing development complexity through sharing the ASIC, hardware, software and DAQ development with existing versions of ePix cameras.Comment: 8 pages, 6 figure

Performance of ePix10K, a high dynamic range, gain auto-ranging pixel detector for FELs

ePix10K is a hybrid pixel detector developed at SLAC for demanding free-electron laser (FEL) applications, providing an ultrahigh dynamic range (245 eV to 88 MeV) through gain auto-ranging. It has three gain modes (high, medium and low) and two auto-ranging modes (high-to-low and medium-to-low). The first ePix10K cameras are built around modules consisting of a sensor flip-chip bonded to 4 ASICs, resulting in 352x384 pixels of 100 $\mu$m x 100 $\mu$m each. We present results from extensive testing of three ePix10K cameras with FEL beams at LCLS, resulting in a measured noise floor of 245 eV rms, or 67 e$^-$ equivalent noise charge (ENC), and a range of 11000 photons at 8 keV. We demonstrate the linearity of the response in various gain combinations: fixed high, fixed medium, fixed low, auto-ranging high to low, and auto-ranging medium-to-low, while maintaining a low noise (well within the counting statistics), a very low cross-talk, perfect saturation response at fluxes up to 900 times the maximum range, and acquisition rates of up to 480 Hz. Finally, we present examples of high dynamic range x-ray imaging spanning more than 4 orders of magnitude dynamic range (from a single photon to 11000 photons/pixel/pulse at 8 keV). Achieving this high performance with only one auto-ranging switch leads to relatively simple calibration and reconstruction procedures. The low noise levels allow usage with long integration times at non-FEL sources. ePix10K cameras leverage the advantages of hybrid pixel detectors with high production yield and good availability, minimize development complexity through sharing the hardware, software and DAQ development with all other versions of ePix cameras, while providing an upgrade path to 5 kHz, 25 kHz and 100 kHz in three steps over the next few years, matching the LCLS-II requirements.Comment: 9 pages, 5 figure

Atomistic characterization of the active-site solvation dynamics of a model photocatalyst

The interactions between the reactive excited state of molecular photocatalysts and surrounding solvent dictate reaction mechanisms and pathways, but are not readily accessible to conventional optical spectroscopic techniques. Here we report an investigation of the structural and solvation dynamics following excitation of a model photocatalytic molecular system [Ir-2(dimen)(4)](2+), where dimen is para-diisocyanomenthane. The time-dependent structural changes in this model photocatalyst, as well as the changes in the solvation shell structure, have been measured with ultrafast diffuse X-ray scattering and simulated with Born-Oppenheimer Molecular Dynamics. Both methods provide direct access to the solute-solvent pair distribution function, enabling the solvation dynamics around the catalytically active iridium sites to be robustly characterized. Our results provide evidence for the coordination of the iridium atoms by the acetonitrile solvent and demonstrate the viability of using diffuse X-ray scattering at free-electron laser sources for studying the dynamics of photocatalysis.1

Response of the ATLAS tile calorimeter prototype to muons

A study of high energy muons traversing the ATLAS hadron Tile calorimeter in the barrel region in the energy range between 10 and 300~GeV is presented. Both test beam experimental data and Monte Carlo simulations are given and show good agreement. The Tile calorimeter capability of detecting isolated muons over the above energy range is demonstrated. A signal to background ratio of about 10 is expected for the nominal LHC luminosity ($10^{34} cm^{-2} sec^{-1}$). The photoelectron statistics effect in the muon shape response is shown. The e/mip ratio is found to be $0.81 \pm 0.03$; the e/$\mu$ ratio is in the range 0.91 - 0.97. The energy loss of a muon in the calorimeter, dominated by the energy lost in the absorber, can be correlated to the energy loss in the active material. This correlation allows one to correct on an event by event basis the muon energy loss in the calorimeter and therefore reduce the low energy tails in the muon momentum distribution

Evaluation of Fermi Read-out of the ATLAS Tilecal Prototype

Prototypes of the \fermi{} system have been used to read out a prototype of the \atlas{} hadron calorimeter in a beam test at the CERN SPS. The \fermi{} read-out system, using a compressor and a 40 MHz sampling ADC, is compared to a standard charge integrating read-out by measuring the energy resolution of the calorimeter separately with the two systems on the same events. Signal processing techniques have been designed to optimize the treatment of \fermi{} data. The resulting energy resolution is better than the one obtained with the standard read-out

Results from a combined test of an electromagnetic liquid argon calorimeter with a hadronic scintillating-tile calorimeter

The first combined test of an electromagnetic liquid argon accordion calorimeter and a hadronic scintillating-tile calorimeter was carried out at the CERN SPS. These devices are prototypes of the barrel calorimeter of the future ATLAS experiment at the LHC. The energy resolution of pions in the energy range from 20 to 300~GeV at an incident angle $\theta$ of about 11$^\circ$ is well-described by the expression \sigma/E = ((46.5 \pm 6.0)\%/\sqrt{E} +(1.2 \pm 0.3)\%) \oplus (3.2 \pm 0.4)~\mbox{GeV}/E. Shower profiles, shower leakage, and the angular resolution of hadronic showers were also studied

Technical considerations about laparoscopic treatment of giant hiatal hernia

Clinica I Chirurgie, Clinica II Chirurgie, Clinica ATI, Spital Clinic Universitar de Urgenţe “Sf.Spiridon”, Iaşi, România, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Hernia hiatală gigantă este definită acea hernie care conține mai mult de o treime din stomac în sacul herniar. Reprezintă în general cam 5-10% din totalul herniilor hiatale, iar distanța dintre pilierii diafragmului este adesea peste 5 cm. Tehnica chirurgicală laparoscopică este metoda terapeutică cea mai bună, însă necesită anumite artificii tehnice. Scopul studiului este de a implementa anumite gesturi chirurgicale în tratamentul laparoscopic al acestei entități. Material și metode: Este un studiu retrospectiv pe 5 ani între ianuarie 2010 și decembrie 2014, realizat în Clinica I Chirurgie, Spital Clinic Universitar de Urgențe “Sf.Spiridon”, Iași. În acest studiu au fost incluși un numar de 32 de pacienți, dintre care 8 hernii hiatale gigantice. Criteriile de includere au fost: pacienți cu peste 1/3 din stomac în sacul de hernie, orificiul herniar peste 5 cm și pacienți care nu au mai fost operați pentru patologie esogastroduodenală. Rezultate: Au existat complicații minore intraoperatorii ce au fost rezolvate (deschiderea pleurei în 4 cazuri cu sutura acesteia și o plagă hepatică la care s-a realizat hemostaza). Postoperator nu au fost complicații locale, controlul cu substanță de contrast făcîndu-se între ziua a 4-a și a 7-a postoperator. A existat un singur caz de pneumonie lobară ce s-a remis sub tratament medical. Particularitățile tehnice au fost cele legate de disecția sacului, închiderea orificiului și efectuarea procedeului antireflux. Concluzii: Un diagnostic precis și bine documentat alături de folosirea unei tehnici adecvate duce la rezultate foarte bune pe termen lung în herniile hiatale gigante.Introduction: Giant hiatal hernia is defined the hernia that contains more than a third of stomach in hernia sac. Generally represents about 5-10% of hiatal hernias and diaphragmatic distance between pillars is often more than 5 cm. Laparoscopic surgical technique provides the best approach, but it requires some technical fireworks. The aim of research is to implement some particular skills in laparoscopic surgical treatment of this entity. Material and methods: It is a 5-year retrospective study between January 2010 and December 2014, conducted in First Surgical Clinic University Emergency Hospital “St.Spiridon”, Iasi. The study includes a total of 32 patients of which 8 were giant hiatal hernias. Inclusion criteria were patients with more than 1/3 of stomach in hernia sac, pillar distance more than 5 cm and patients who have not been operated for an esogastroduodenal pathology. Results: There were minor intraoperative complications that were resolved (opening pleura in 4 cases with its suture and wound liver who achieved hemostasis). There were no major postoperative complication and local control with contrast being made between 4th and 7th postoperative day. There was one case of lobar pneumonia which was resolved under medical treatment. Technical peculiarities were related to sac dissection, closing the defect and making anti-reflux procedure. Conclusions: An accurate and documented diagnosis with the use of appropriate techniques lead to very good results in the long term of giant hiatal hernias