Energy Recovery Linac: Vacuum

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Biostratigraphy of Middle and Late Pennsylvanian (Desmoinesian-Virgilian) ammonoids

New stratigraphic ranges for genera of Desmoinesian-Virgilian ammonoids are presented, based on analysis of 40,000 specimens collected from over 70 ammonoid-bearing horizons that represent at least 40 successive stratigraphic levels in the North American midcontinent. These range revisions indicate that current generic-level ammonoid zonations are inadequate, especially for correlation of Pennsylvanian series and stage boundaries. Six high-confidence, largely generic-level first-occurrence zones are proposed for the Desmoinesian through Virgilian stages: Wellerites Zone, Eothalassoceras Zone, Pennoceras Zone, Preshumardites Zone, Pseudaktubites Zone, and Shumardites Zone. Fifteen zones of lesser confidence for correlation are also suggested. The Shumarditidae Plummer & Scott, 1937, is emended to include Preshumardites Plummer & Scott, 1937, Pseudaktubites gen. nov. (type species, Preshumardites stainbrooki Plummer & Scott, 1937), and Shumardites Smith, 1903. Early Permian (Sakmarian) species previously assigned to Preshumardites are reassigned to Andrianovia gen. nov. (type species ?Preshumardites sakmarae Ruzhencev, 1938). Aktubites Ruzhencev, 1955, Eoshumardites Popov, 1960, and Parashumardites Ruzhencev, 1939, previously included in the Shumarditidae, are assigned to the new family Parashumarditidae. Eovidrioceras inexpectans gen. nov., sp. nov. is included and is interpreted as the ancestor of the cyclobacean family Vidrioceratidae Plummer & Scott, 1937. The base of the revised Wellerites Zone, defined by the first occurrence of the nominate genus, approximates but does not coincide with the Atokan-Desmoinesian boundary. Recorrelation of the stratigraphic level of the Collinsville, Oklahoma, ammonoid locality from the "Seminole Formation" (basal Missourian) to the Holdenville Formation (upper Desmoinesian), based on lithostratigraphic evidence, effectively places the first occurrence of Eothalassoceras in the upper Desmoinesian. Because Wellerites apparently became extinct before the end of the Desmoinesian, the revised Eothalassoceras Zone is used to represent the upper Desmoinesian. The Middle-Upper Pennsylvanian boundary (Desmoinesian-Missourian boundary) can be recognized by the appearance of Pennoceras, which defines the base of the new Pennoceras Zone. The Pennoceras Zone is an excellent indicator of lower Missourian strata in the northern midcontinent, north-central Texas, the Marathon Uplift, and the Appalachian Basin. The new Preshumardites Zone occupies most of the upper part of the Missourian Stage. The appearance of the ancestral shumarditid Pseudaktubites, which defines the base of the new Pseudaktubites Zone, occurs one cycle below the Missourian-Virgilian boundary, which is currently recognized at the top of the South Bend Limestone Member in eastern Kansas. No recognizable biostratigraphic event coincides with the South Bend Member, thereby resulting in an uncorrelatable chronostratigraphic boundary. The largest changeover in ammonoid faunas takes place at the base of strata containing the upper part of the Pseudaktubites Zone (Pseudaktubites stainbrooki Subzone). The base of the Pseudaktubites stainbrooki Subzone is stratigraphically near the original Missourian-Virgilian boundary. It is recommended that the stratigraphic level containing the base of the Pseudaktubites stainbrooki Subzone be adopted as the official base of the Virgilian Stage. Recognition of the upper subzone of the Pseudaktubites Zone (Pseudaktubites stainbrooki Subzone) within the Colony Creek Shale Member in north-central Texas places the base of the Virgilian within the upper part of the Canyon Group and substantially below the current position at the Canyon-Cisco group boundary. Shumardites, a taxon previously used to mark the base of the Virgilian Stage, appears in early middle Virgilian strata; consequently, the revised Shumardites Zone represents the middle-upper Virgilian interval

The skill of atmospheric linear inverse models in hindcasting the Madden–Julian Oscillation

A suite of statistical atmosphere-only linear inverse models of varying complexity are used to hindcast recent MJO events from the Year of Tropical Convection and the Cooperative Indian Ocean Experiment on Intraseasonal Variability/Dynamics of the Madden–Julian Oscillation mission periods, as well as over the 2000–2009 time period. Skill exists for over two weeks, competitive with the skill of some numerical models in both bivariate correlation and root-mean-squared-error scores during both observational mission periods. Skill is higher during mature Madden–Julian Oscillation conditions, as opposed to during growth phases, suggesting that growth dynamics may be more complex or non-linear since they are not as well captured by a linear model. There is little prediction skill gained by including non-leading modes of variability.National Science Foundation (U.S.) (Grant 0731520)United States. Office of Naval Research (Grants N00014-10-1-0541, N00014-13-1-0139 and N00014-13-1-0704)National Science Foundation (U.S.) (Grant OCE-0960770

Biostratigraphy of Middle and Late Pennsylvanian (Desmoinesian-Virgilian) ammonoids

New stratigraphic ranges for genera of Desmoinesian-Virgilian ammonoids are presented, based on analysis of 40,000 specimens collected from over 70 ammonoid-bearing horizons that represent at least 40 successive stratigraphic levels in the North American midcontinent. These range revisions indicate that current generic-level ammonoid zonations are inadequate, especially for correlation of Pennsylvanian series and stage boundaries. Six high-confidence, largely generic-level first-occurrence zones are proposed for the Desmoinesian through Virgilian stages: Wellerites Zone, Eothalassoceras Zone, Pennoceras Zone, Preshumardites Zone, Pseudaktubites Zone, and Shumardites Zone. Fifteen zones of lesser confidence for correlation are also suggested. The Shumarditidae Plummer & Scott, 1937, is emended to include Preshumardites Plummer & Scott, 1937, Pseudaktubites gen. nov. (type species, Preshumardites stainbrooki Plummer & Scott, 1937), and Shumardites Smith, 1903. Early Permian (Sakmarian) species previously assigned to Preshumardites are reassigned to Andrianovia gen. nov. (type species ?Preshumardites sakmarae Ruzhencev, 1938). Aktubites Ruzhencev, 1955, Eoshumardites Popov, 1960, and Parashumardites Ruzhencev, 1939, previously included in the Shumarditidae, are assigned to the new family Parashumarditidae. Eovidrioceras inexpectans gen. nov., sp. nov. is included and is interpreted as the ancestor of the cyclobacean family Vidrioceratidae Plummer & Scott, 1937. The base of the revised Wellerites Zone, defined by the first occurrence of the nominate genus, approximates but does not coincide with the Atokan-Desmoinesian boundary. Recorrelation of the stratigraphic level of the Collinsville, Oklahoma, ammonoid locality from the "Seminole Formation" (basal Missourian) to the Holdenville Formation (upper Desmoinesian), based on lithostratigraphic evidence, effectively places the first occurrence of Eothalassoceras in the upper Desmoinesian. Because Wellerites apparently became extinct before the end of the Desmoinesian, the revised Eothalassoceras Zone is used to represent the upper Desmoinesian. The Middle-Upper Pennsylvanian boundary (Desmoinesian-Missourian boundary) can be recognized by the appearance of Pennoceras, which defines the base of the new Pennoceras Zone. The Pennoceras Zone is an excellent indicator of lower Missourian strata in the northern midcontinent, north-central Texas, the Marathon Uplift, and the Appalachian Basin. The new Preshumardites Zone occupies most of the upper part of the Missourian Stage. The appearance of the ancestral shumarditid Pseudaktubites, which defines the base of the new Pseudaktubites Zone, occurs one cycle below the Missourian-Virgilian boundary, which is currently recognized at the top of the South Bend Limestone Member in eastern Kansas. No recognizable biostratigraphic event coincides with the South Bend Member, thereby resulting in an uncorrelatable chronostratigraphic boundary. The largest changeover in ammonoid faunas takes place at the base of strata containing the upper part of the Pseudaktubites Zone (Pseudaktubites stainbrooki Subzone). The base of the Pseudaktubites stainbrooki Subzone is stratigraphically near the original Missourian-Virgilian boundary. It is recommended that the stratigraphic level containing the base of the Pseudaktubites stainbrooki Subzone be adopted as the official base of the Virgilian Stage. Recognition of the upper subzone of the Pseudaktubites Zone (Pseudaktubites stainbrooki Subzone) within the Colony Creek Shale Member in north-central Texas places the base of the Virgilian within the upper part of the Canyon Group and substantially below the current position at the Canyon-Cisco group boundary. Shumardites, a taxon previously used to mark the base of the Virgilian Stage, appears in early middle Virgilian strata; consequently, the revised Shumardites Zone represents the middle-upper Virgilian interval

R&D ERL: Vacuum

The ERL Vacuum systems are depicted in a figure. ERL has eight vacuum volumes with various sets of requirements. A summary of vacuum related requirements is provided in a table. Five of the eight volumes comprise the electron beamline. They are the 5-cell Superconducting RF Cavity, Superconducting e-gun, injection, loop and beam dump. Two vacuum regions are the individual cryostats insulating the 5-cell Superconducting RF Cavity and the Superconducting e-gun structures. The last ERL vacuum volume not shown in the schematic is the laser transport line. The beamline vacuum regions are separated by electropneumatic gate valves. The beam dump is common with loop beamline but is considered a separate volume due to geometry and requirements. Vacuum in the 5-cell SRF cavity is maintained in the {approx}10{sup -9} torr range at room temperature by two 20 l/s ion pumps and in the e-gun SRF cavity by one 60 l/s ion pump. Vacuum in the SRF cavities operated at 2{sup o}K is reduced to low 10{sup -11} torr via cryopumping of the cavity walls. The cathode of the e-gun must be protected from poisoning, which can occur if vacuum adjacent to the e-gun in the injection line exceeds 10-11 torr range in the injection warm beamline near the e-gun exit. The vacuum requirements for beam operation in the loop and beam dump are 10-9 torr range. The beamlines are evacuated from atmospheric pressure to high vacuum level with a particulate free, oil free turbomolecular pumping cart. 25 l/s shielded ion pumps distributed throughout the beamlines maintain the vacuum requirement. Due to the more demanding vacuum requirement of the injection beamline proximate to the e-gun, a vacuum bakeout of the injection beamline is required. In addition, two 200 l/s diode ion pumps and supplemental pumping provided by titanium sublimation pumps are installed in the injection line just beyond the exit of the e-gun. Due to expected gas load a similar pumping arrangement is planned for the beam dump. The cryostat vacuum thermally insulating the SRF cavities need only reduce the convective heat load such that heat loss is primarily radiation through several layers of multi-layer insulation and conductive end-losses which are contained by 5{sup o}K thermal transitions. Prior to cool down rough vacuum {approx}10{sup -5} torr range is established and maintained by a dedicated turbomolecular pump station. Cryopumping by the cold mass and heat shields reduces the insulating vacuum to 10{sup -7} torr range after cool down

R&D ERL: Vacuum

The ERL Vacuum systems are depicted in a figure. ERL has eight vacuum volumes with various sets of requirements. A summary of vacuum related requirements is provided in a table. Five of the eight volumes comprise the electron beamline. They are the 5-cell Superconducting RF Cavity, Superconducting e-gun, injection, loop and beam dump. Two vacuum regions are the individual cryostats insulating the 5-cell Superconducting RF Cavity and the Superconducting e-gun structures. The last ERL vacuum volume not shown in the schematic is the laser transport line. The beamline vacuum regions are separated by electropneumatic gate valves. The beam dump is common with loop beamline but is considered a separate volume due to geometry and requirements. Vacuum in the 5-cell SRF cavity is maintained in the {approx}10{sup -9} torr range at room temperature by two 20 l/s ion pumps and in the e-gun SRF cavity by one 60 l/s ion pump. Vacuum in the SRF cavities operated at 2{sup o}K is reduced to low 10{sup -11} torr via cryopumping of the cavity walls. The cathode of the e-gun must be protected from poisoning, which can occur if vacuum adjacent to the e-gun in the injection line exceeds 10-11 torr range in the injection warm beamline near the e-gun exit. The vacuum requirements for beam operation in the loop and beam dump are 10-9 torr range. The beamlines are evacuated from atmospheric pressure to high vacuum level with a particulate free, oil free turbomolecular pumping cart. 25 l/s shielded ion pumps distributed throughout the beamlines maintain the vacuum requirement. Due to the more demanding vacuum requirement of the injection beamline proximate to the e-gun, a vacuum bakeout of the injection beamline is required. In addition, two 200 l/s diode ion pumps and supplemental pumping provided by titanium sublimation pumps are installed in the injection line just beyond the exit of the e-gun. Due to expected gas load a similar pumping arrangement is planned for the beam dump. The cryostat vacuum thermally insulating the SRF cavities need only reduce the convective heat load such that heat loss is primarily radiation through several layers of multi-layer insulation and conductive end-losses which are contained by 5{sup o}K thermal transitions. Prior to cool down rough vacuum {approx}10{sup -5} torr range is established and maintained by a dedicated turbomolecular pump station. Cryopumping by the cold mass and heat shields reduces the insulating vacuum to 10{sup -7} torr range after cool down

Transition from suppressed to active convection modulated by a weak-temperature gradient derived large-scale circulation

Numerical simulations are performed to assess the influence of the large-scale circulation on the transition from suppressed to active convection. As a model tool, we used a coupled-column model. It consists of two cloud-resolving models which are fully coupled via a large-scale circulation which is derived from the requirement that the instantaneous domain-mean potential temperature profiles of the two columns remain close to each other. This is known as the weak-temperature gradient approach. The simulations of the transition are initialized from coupled-column simulations over non-uniform surface forcing and the transition is forced within the dry column by changing the local and/or remote surface forcings to uniform surface forcing across the columns. As the strength of the circulation is reduced to zero, moisture is recharged into the dry column and a transition to active convection occurs once the column is sufficiently moistened to sustain deep convection. Direct effects of changing surface forcing occur over the first few days only. Afterward, it is the evolution of the large-scale circulation which systematically modulates the transition. Its contributions are approximately equally divided between the heating and moistening effects. A transition time is defined to summarize the evolution from suppressed to active convection. It is the time when the rain rate within the dry column is halfway to the mean value obtained at equilibrium over uniform surface forcing. The transition time is around twice as long for a transition that is forced remotely compared to a transition that is forced locally. Simulations in which both local and remote surface forcings are changed produce intermediate transition times

Using the weak-temperature gradient approximation to evaluate parameterizations: an example of the transition from suppressed to active convection

Two single-column models are fully coupled via the weak-temperature gradient approach. The coupled-SCM is used to simulate the transition from suppressed to active convection under the influence of an interactive large-scale circulation. The sensitivity of this transition to the value of mixing entrainment within the convective parameterization is explored. The results from these simulations are compared with those from equivalent simulations using coupled cloud-resolving models. Coupled-column simulations over non-uniform surface forcing are used to initialize the simulations of the transition, in which the column with suppressed convection is forced to undergo a transition to active convection by changing the local and/or remote surface forcings. The direct contributions from the changes in surface forcing are to induce a weakening of the large-scale circulation which systematically modulates the transition. In the SCM, the contributions from the large-scale circulation are dominated by the heating effects, while in the CRM the heating and moistening effects are about equally divided. A transition time is defined as the time when the rain rate in the dry column is halfway to the value at equilibrium after the transition. For the control value of entrainment, the order of the transition times is identical to that obtained in the CRM, but the transition times are markedly faster. The locally forced transition is strongly delayed by a higher entrainment. A consequence is that for a 50% higher entrainment the transition times are reordered. The remotely forced transition remains fast while the locally forced transition becomes slow, compared to the CRM