U. Akgun

Radiation-hardness studies of high OH- content quartz fibres irradiated with 500 MeV electrons

We investigated darkening of nine fiber types while irradiated with 500 MeV electrons of the Linac injector of LEP (LIL) at CERN. The transmission of Xe light by irradiated fibers was measured in-situ in 350-750 nm range. The induced attenuation at 450 nm is typically (1.52 + 0.15) dB/m for a 100 Mrad absorbed dose. Two-parameter fits for darkening and recovery are presented. After irradiation the tensile strength of the samples remain essentially unchanged. A tensile strength of (4.94 + 0.37) GPa was measured for Polymicro quartz fibers.

Afterpulse timing and rate investigation of three different Hamamatsu Photomultiplier Tubes

We present the results of the tests performed on 90 photomultiplier tubes (PMT) to characterize their afterpulses. Three different types of H amamatsu PMTs (R7525, R6427, and R1398) were studied for their afterpulse rates and timings at different incident light intensities and gain values, at the University of Iowa PMT test station. Afterpulse rates show slight increase with the PMT gain, but there is almost no dependence on incident light intensity. Three specific time delays are determined for the afterpulses, and their indivi dual rate contributions are characterized. The results from manufacturers independent tests on R7525 PMTs are reported, as well. The possible effects of these afterpulses on the future hadron c ollider experiments are also discussed.

Comparison of PMTs from three different manufacturers for the CMS-HF forward calorimeter

The builders of the CMS forward hadron calorimeter established a set of specifications for readout PMTs that reflected the physics goals and mechanical needs of the CMS experiment. Three manufacturers, Hamamatsu, Photonis (Philips), and Electron Tubes (EMI), provided candidate PMTs based on these initial requirements. Timing, gain, dark current properties, and single photoelectron spectra of these candidate PMTs were measured. Results show that Hamamatsu PMTs (R7525HA) conform best to the specifications of the Hadron-Forward (HF) Calorimeter.

Periplasmic vestibule plays an important role for solute recruitment, selectivity, and gating in the Rh/Amt/MEP superfamily

AmtB, a member of the Rh/Amt/MEP superfamily, is responsible for ammonia transport in Escherichia coli. The ammonia pathway in AmtB consists of a narrow hydrophobic lumen in between hydrophilic periplasmic and cytoplasmic vestibules. A series of molecular dynamics simulations (greater than 0.4 μs in total) were performed to determine the mechanism of solute recruitments and selectivity by the periplasmic vestibule. The results show that the periplasmic vestibule plays a crucial role in solute selectivity, and its solute preferences follow the order of . Based on our results, recruitment is initiated by its interaction with either E70 or E225, highly conserved residues located at the entrance of the vestibule. Subsequently, the backbone carbonyl groups at the periplasmic vestibule direct to the conserved aromatic cage at the bottom of the vestibule (known as the Am1 site). The umbrella sampling simulations suggest that the conserved residue D160 is not directly involved in the ammonia conduction; rather its main function is to keep the structure of periplasmic vestibule intact. The MD simulations also revealed that two partially stacked phenyl rings of F107 and F215, separating the periplasmic vestibule from the hydrophobic lumen, flip open and closed simultaneously with a frequency of approximately 108 flipping events per second. These results show how the periplasmic vestibule selectively recruits to the Am1 site, and also that the synchronized flipping of two phenyl rings potentially facilitates the solute transition from the periplasmic vestibule to the hydrophobic lumen in the Rh/Amt/MEP superfamily.

CMS Hadronic EndCap Calorimeter Upgrade Studies for SLHC “Čerenkov Light Collection From Quartz Plates”

Due to an expected increase in radiation damage under super-LHC conditions, we propose to substitute the scintillator tiles in the original design of the hadronic endcap (HE) calorimeter with quartz plates. Quartz is shown to be radiation hard. Using wavelength shifting fibers, it is possible to collect efficiently the Cerenkov light generated in quartz plates. This paper summarizes the results from various test beams, bench tests, and Geant4 simulations done on methods of collecting light from quartz plates, as well as radiation hardness tests on quartz material.

CMS Hadronic Endcap Calorimeter Upgrade Studies for SLHC “P-Terphenyl Deposited Quartz Plate Calorimeter Prototype”

The Large Hadron Collider (LHC) is going to start taking data with 1033 cm-2s-1 luminosity, and reach the designed value of 1034 cm-2s-1 in 2013. The LHC luminosity will continue to improve each year, reaching to 1035 cm-2s-1 in 2023. We call this high luminosity era the Super-LHC (SLHC). Hadronic Endcap (HE) calorimeters of the CMS experiment cover the pseudorapidity range of 1.4 ≪ η ≪ 3 on both sides of the CMS detector, contributing to superior jet and missing transverse energy resolutions. As the integrated luminosity of the LHC increases, the scintillator tiles used in the CMS Hadronic Endcap calorimeter will lose their efficiency. The CMS collaboration plans to substitute Quartz plates for the scintillator tiles of the original design. Various tests have proved Quartz to be radiation hard, but the light produced by Quartz comes from Cerenkov process, which yields drastically fewer photons than scintillation. To increase the light collection efficiency, we propose to treat the Quartz plates with radiation hard wavelength shifters, p-terphenyl or 4% gallium doped zinc oxide. The test beam studies revealed a substantial light collection increase on pTp or ZnO:Ga deposited Quartz plates. We constructed a 20 layer calorimeter prototype with pTp coated plates, and tested the hadronic and the electromagnetic capabilities at the CERN H2 area. Here we report the results of these test beams as well as radiation damage studies performed on p-Terphenyl.

Quartz plate calorimeter as SLHC upgrade to CMS hadronic endcap calorimeters

Due to an expected increase in radiation damage under super-LHC conditions, we propose to substitute the scintillator tiles in the original design of the hadronic endcap (HE) calorimeter with quartz plates. Quartz is proved to be radiation hard by the radiation damage tests with electron, proton, neutron and gamma beams. Using wavelength shifting fibers, it is possible to collect efficiently the Cherenkov light generated in quartz plates. This paper summarizes the results from various test beams, bench tests, and Geant4 simulations done on methods of collecting light from quartz plates, as well as radiation hardness tests on quartz material.

Forward Neutron Production at the Fermilab Main Injector

We have measured cross sections for forward neutron production from a variety of targets using proton beams from the Fermilab Main Injector. Measurements were performed for proton beam momenta of 58, 84, and 120 GeV/c. The cross section dependence on the atomic weight (A) of the targets was found to vary as A{sup {alpha}}, where {alpha} is 0.46{+-}0.06 for a beam momentum of 58 GeV/c and 0.54{+-}0.05 for 120 GeV/c. The cross sections show reasonable agreement with FLUKA and DPMJET Monte Carlos. Comparisons have also been made with the LAQGSM Monte Carlo.

Charged kaon mass measurement using the Cherenkov effect

The two most recent and precise measurements of the charged kaon mass use X-rays from kaonic atoms and report uncertainties of 14 ppm and 22 ppm yet dier from each other by 122 ppm. We describe the possibility of an independent mass measurement using the measurement of Cherenkov light from a narrow-band beam of kaons, pions, and protons. This technique was demonstrated using data taken opportunistically by the Main Injector Particle Production experiment at Fermi National Accelerator Laboratory which recorded beams of protons, kaons, and pions ranging in momentum from +37 GeV/c to +63 GeV/c. The measured value is 491.3 1.7 MeV/c 2 , which is within 1.4 of the world average. An improvement of two orders of magnitude in precision would make this technique useful for resolving the ambiguity in the X-ray data and may be achievable in a dedicated experiment.

Characterizing the binding interactions between P-glycoprotein and eight known cardiovascular transport substrates

The multidrug efflux pump P‐glycoprotein (Pgp) is upregulated in cardiomyocytes following chronic ischemia from infarction and hypoxia caused by sleep apnea. This report summarizes the molecular dynamic studies performed on eight cardiovascular drugs to determine their corresponding binding sites on mouse Pgp. Selected Pgp transport ligands include: Amiodarone, Bepridil, Diltiazem, Dipyridamole, Nicardipine, Nifedipine, Propranolol, and Quinidine. Extensive molecular dynamic equilibration simulations were performed to determine drug docking interactions. Distinct binding sites were not observed, but rather a binding belt was seen with multiple residues playing a role in each studied drugs stable docking. Three key drug–protein interactions were identified: hydrogen bonding, hydrophobic packing, and the formation of a “cage” of aromatic residues around the drug. After drug stabilization, water molecules were observed to leak into the binding belt and condense around the drug. Water influx into the binding domain of Pgp may play a role in catalytic transition and drug expulsion. The cytoplasmic recruitment theory was also tested, and the drugs were observed to interact with conserved loops of residues with a strong affinity. A free energy change of astronomical value is required to recruit the drug from the cytoplasm to the binding belt within the transmembrane domain of Pgp.