197 research outputs found
Zero differential resistance state of two dimensional electron systems in strong magnetic fields
Zero differential resistance state is found in response to direct current
applied to 2D electron systems at strong magnetic field and low temperatures.
Transition to the state is accompanied by sharp dip of negative differential
resistance, which occurs above threshold value of the direct current.
The state depends significantly on the temperature and is not observable above
several Kelvins. Additional analysis shows lack of the linear stability of the
2D electron systems at and inhomogeneous, non-stationary pattern of
the electric current in the zero differential resistance state. We suggest that
the dc bias induced redistribution of the 2D electrons in energy space is the
dominant mechanism leading to the new electron state.Comment: 5 pages, 3 figure
Electrode Strip Deposition for the CMS Barrel Drift Tube System
The full production ideation, design, set up and realization of the Electrode Strip Deposition for the entire construction of the CMS Barrel Drift Tube System are described in detail
EUV spectra of highly-charged ions W-W relevant to ITER diagnostics
We report the first measurements and detailed analysis of extreme ultraviolet
(EUV) spectra (4 nm to 20 nm) of highly-charged tungsten ions W to
W obtained with an electron beam ion trap (EBIT). Collisional-radiative
modelling is used to identify strong electric-dipole and magnetic-dipole
transitions in all ionization stages. These lines can be used for impurity
transport studies and temperature diagnostics in fusion reactors, such as ITER.
Identifications of prominent lines from several W ions were confirmed by
measurement of isoelectronic EUV spectra of Hf, Ta, and Au. We also discuss the
importance of charge exchange recombination for correct description of
ionization balance in the EBIT plasma.Comment: 11 pages, 4 figure
Performance of the CMS Cathode Strip Chambers with Cosmic Rays
The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device
in the CMS endcaps. Their performance has been evaluated using data taken
during a cosmic ray run in fall 2008. Measured noise levels are low, with the
number of noisy channels well below 1%. Coordinate resolution was measured for
all types of chambers, and fall in the range 47 microns to 243 microns. The
efficiencies for local charged track triggers, for hit and for segments
reconstruction were measured, and are above 99%. The timing resolution per
layer is approximately 5 ns
Design, performance, and calibration of CMS forward calorimeter wedges
We report on the test beam results and calibration methods using high energy electrons, pions and muons with the CMS forward calorimeter (HF). The HF calorimeter covers a large pseudorapidity region (3 <= vertical bar eta vertical bar <= 5), and is essential for a large number of physics channels with missing transverse energy. It is also expected to play a prominent role in the measurement of forward tagging jets in weak boson fusion channels in Higgs production. The HF calorimeter is based on steel absorber with embedded fused-silica-core optical fibers where Cherenkov radiation forms the basis of signal generation. Thus, the detector is essentially sensitive only to the electromagnetic shower core and is highly non-compensating (e/h approximate to 5). This feature is also manifest in narrow and relatively short showers compared to similar calorimeters based on ionization. The choice of fused-silica optical fibers as active material is dictated by its exceptional radiation hardness. The electromagnetic energy resolution is dominated by photoelectron statistics and can be expressed in the customary form as a/root E circle plus b. The stochastic term a is 198% and the constant term b is 9%. The hadronic energy resolution is largely determined by the fluctuations in the neutral pion production in showers, and when it is expressed as in the electromagnetic case, a = 280% and b = 11%
ĐОдоНиŃОванио ĐżŃОйогОв и пОŃĐľŃŃ ŃноŃгии вŃŃОкОŃноŃгоŃиŃĐľŃĐşĐ¸Ń Đ¸ĐžĐ˝ĐžĐ˛ в ОднОŃНОКнŃŃ Đ¸ ПнОгОŃНОКнŃŃ ĐźĐ°ŃĐľŃиаНаŃ
Linear and mass ranges of protons and argon ions in aluminum, alumina, bismuth, and W77.7Cu22.3 composite shields were calculated using the SRIM software package. It is shown that the protection efficiency against high-energy ions by materials with large atomic charge (Z) values is higher, from the position of linear ranges of particles, and lower, from the position of mass ranges, in comparison with materials with low Z values. The dependence of the threshold energy on the serial number of particles for aluminum, bismuth, and composite W77.7Cu22.3 shields is determined. The ionization loss spectra for the passage of both protons with an energy of 20 MeV and krypton ions with an energy of 7.75 GeV through multilayer Bi/Al/Al2O3 and Al/Al2O3/Bi structures were calculated. These results showed that the braking of high-energy particles in the case when the first layer contains a heavy element is higher than in the case when the first layer contains a light element. The influence of the sequence in the arrangement and thickness of the layers in the multilayer structures of the Bi/Al/Al2O3 system on the efficiency of protection against high-energy ions was studied. It is shown that the nature of the dependences R(E) and ion energy losses are determined by the sequence of arrangement of individual layers, which is due to the difference in the conversion of the spectra by the material of the first layer. The studied radiation shields can be used in aerospace and nuclear technologies, as well as in many scientific and medical devices, and can be used to protect against the effects of a wide range of ionizing radiation (electrons, protons, heavy charged particles, etc.).ĐĄ пОПОŃŃŃ ĐżŃОгŃаППнОгО кОПпНокŃĐ° SRIM ŃĐ°ŃŃŃиŃĐ°Đ˝Ń ĐťĐ¸Đ˝ĐľĐšĐ˝ŃĐľ и ПаŃŃОвŃĐľ ĐżŃОйоги ĐżŃĐžŃОнОв и иОнОв Đ°ŃгОна в ŃĐşŃанаŃ
иС Đ°ĐťŃПиниŃ, ОкŃида Đ°ĐťŃПиниŃ, виŃĐźŃŃĐ° и кОПпОСиŃĐ° W77,7Cu22,3. ĐОкаСанО, ŃŃĐž ŃŃŃокŃивнОŃŃŃ ĐˇĐ°ŃиŃŃ ĐžŃ Đ˛ŃŃОкОŃноŃгоŃиŃĐľŃкиŃ
иОнОв ПаŃĐľŃиаНаПи Ń ĐąĐžĐťŃŃиПи СнаŃониŃПи СаŃŃĐ´Đ° ŃĐ´ĐľŃ Đ°ŃОПОв (Z) вŃŃĐľ Ń ĐżĐžĐˇĐ¸Ńии НиноКнŃŃ
ĐżŃОйогОв ŃĐ°ŃŃĐ¸Ń Đ¸ ниМо Ń ĐżĐžĐˇĐ¸Ńии ПаŃŃОвŃŃ
ĐżŃОйогОв, ŃоП ПаŃĐľŃиаНаПи Ń Đ˝Đ¸ĐˇĐşĐ¸ĐźĐ¸ СнаŃониŃПи Z. ĐĐżŃодоНона СавиŃиПОŃŃŃ ĐżĐžŃОгОвОК ŃноŃгии ĐžŃ Z вŃŃОкОŃноŃгоŃиŃĐľŃкиŃ
иОнОв Đ´ĐťŃ ŃĐşŃанОв иС Đ°ĐťŃПиниŃ, виŃĐźŃŃĐ° и кОПпОСиŃĐ° W77,7Cu22,3. ĐŃĐžĐ˛ĐľĐ´ĐľĐ˝Ń ŃĐ°ŃŃĐľŃŃ ŃпокŃŃОв пОŃĐľŃŃ Đ˝Đ° иОниСаŃĐ¸Ń ĐżŃи ĐżŃĐžŃ
ОМдонии ĐżŃĐžŃОнОв Ń ŃноŃгиоК 20 ĐŃРи иОнОв ĐşŃипŃОна Ń ŃноŃгиоК 7,75 ĐŃĐ ŃĐľŃоС ПнОгОŃНОКнŃĐľ ŃŃŃŃĐşŃŃŃŃ Bi/Al/Al2O3 и Al/Al2O3/Bi. Đ Đ°ŃŃĐľŃŃ ĐżĐžĐşĐ°ĐˇĐ°ĐťĐ¸, ŃŃĐž ŃĐžŃПОМонио вŃŃОкОŃноŃгоŃиŃĐľŃкиŃ
ŃĐ°ŃŃĐ¸Ń Đ˛ ŃĐťŃŃĐ°Đľ, кОгда поŃвŃĐš ŃНОК ŃОдоŃĐśĐ¸Ń ŃŃМоНŃĐš ŃНоПонŃ, вŃŃĐľ, ŃоП в ŃĐťŃŃĐ°Đľ, кОгда поŃвŃĐš ŃНОК ŃОдоŃĐśĐ¸Ń ĐťĐľĐłĐşĐ¸Đš ŃНоПонŃ. ĐСŃŃонО вНиŃнио пОŃНодОваŃоНŃнОŃŃи в ŃĐ°ŃпОНОМонии и ŃОНŃĐ¸Đ˝Ń ŃНОов в ПнОгОŃНОКнŃŃ
ŃŃŃŃĐşŃŃŃĐ°Ń
ŃиŃŃĐľĐźŃ Bi/Al/Al2O3 на ŃŃŃокŃивнОŃŃŃ ĐˇĐ°ŃиŃŃ ĐžŃ Đ˛ŃŃОкОŃноŃгоŃиŃĐľŃкиŃ
иОнОв. ĐОкаСанО, ŃŃĐž Ń
Đ°ŃĐ°ĐşŃĐľŃ ĐˇĐ°Đ˛Đ¸ŃиПОŃŃоК R(E) и пОŃĐľŃŃ ŃноŃгии иОнОв ОпŃодоНŃĐľŃŃŃ ĐžŃĐľŃоднОŃŃŃŃ ŃĐ°ŃĐżĐžĐťĐžĐśĐľĐ˝Đ¸Ń ĐžŃдоНŃĐ˝ŃŃ
ŃНОов, ŃŃĐž ŃвŃСанО Ń ŃаСНиŃиоП ĐżŃоОйŃĐ°ĐˇĐžĐ˛Đ°Đ˝Đ¸Ń ŃпокŃŃОв ПаŃĐľŃиаНОП поŃвОгО ŃНОŃ. Đ Đ°ŃŃПОŃŃоннŃĐľ ŃĐşŃĐ°Đ˝Ń ŃадиаŃиОннОК СаŃиŃŃ ĐźĐžĐłŃŃ ĐąŃŃŃ Đ¸ŃпОНŃĐˇĐžĐ˛Đ°Đ˝Ń Đ˛ ŃНоПонŃĐ°Ń
и аппаŃĐ°ŃŃŃĐľ ŃакоŃнО-кОŃПиŃĐľŃкОК ŃĐľŃ
ники, ПОгŃŃ ĐžĐąĐľŃпоŃиŃŃ ŃŃĐľĐąĐžĐ˛Đ°Đ˝Đ¸Ń ĐżĐž ŃŃŃОКŃивОŃŃи Đş вОСдоКŃŃĐ˛Đ¸Ń ŃаСНиŃĐ˝ŃŃ
видОв иОниСиŃŃŃŃиŃ
иСНŃŃониК (ŃНокŃŃОннОо, ĐżŃĐžŃОннОо, гаППа-иСНŃŃонио, ŃŃМоНŃĐľ СаŃŃМоннŃĐľ ŃĐ°ŃŃиŃŃ Đ¸ Đ´Ń.)
Performance and Operation of the CMS Electromagnetic Calorimeter
The operation and general performance of the CMS electromagnetic calorimeter
using cosmic-ray muons are described. These muons were recorded after the
closure of the CMS detector in late 2008. The calorimeter is made of lead
tungstate crystals and the overall status of the 75848 channels corresponding
to the barrel and endcap detectors is reported. The stability of crucial
operational parameters, such as high voltage, temperature and electronic noise,
is summarised and the performance of the light monitoring system is presented
Design, Performance and Calibration of the CMS Forward Calorimeter Wedges
We report on the test beam results and calibration methods using charged particles of the CMS Forward Calorimeter (HF). The HF calorimeter covers a large pseudorapidity region (3\l |\eta| \le 5), and is essential for large number of physics channels with missing transverse energy. It is also expected to play a prominent role in the measurement of forward tagging jets in weak boson fusion channels. The HF calorimeter is based on steel absorber with embedded fused-silica-core optical fibers where Cherenkov radiation forms the basis of signal generation. Thus, the detector is essentially sensitive only to the electromagnetic shower core and is highly non-compensating (e/h \approx 5). This feature is also manifest in narrow and relatively short showers compared to similar calorimeters based on ionization. The choice of fused-silica optical fibers as active material is dictated by its exceptional radiation hardness. The electromagnetic energy resolution is dominated by photoelectron statistics and can be expressed in the customary form as a/\sqrt{E} + b. The stochastic term a is 198% and the constant term b is 9%. The hadronic energy resolution is largely determined by the fluctuations in the neutral pion production in showers, and when it is expressed as in the electromagnetic case, a = 280% and b = 11%
Design, Performance, and Calibration of CMS Hadron-Barrel Calorimeter Wedges
Extensive measurements have been made with pions, electrons and muons on four production wedges of the Compact Muon Solenoid (CMS) hadron barrel (HB) calorimeter in the H2 beam line at CERN with particle momenta varying from 20 to 300 GeV/c. Data were taken both with and without a prototype electromagnetic lead tungstate crystal calorimeter (EB) in front of the hadron calorimeter. The time structure of the events was measured with the full chain of preproduction front-end electronics running at 34 MHz. Moving-wire radioactive source data were also collected for all scintillator layers in the HB. These measurements set the absolute calibration of the HB prior to first pp collisions to approximately 4%
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