Designing the RAL Tier-1 Network for HL-LHC and Future data lakes

The Rutherford Appleton Laboratory (RAL) runs the UK Tier-1 which supports all the LHC experiments, as well as a growing number of others in HEP, Astronomy and Space Science. In September 2020, RAL was provided with funds to upgrade its network. The Tier-1 not only wants to meet the demands of LHC Run 3, it also wants to ensure that it can take an active role in data lake development and the network data challenges in the preparation for HL-LHC. It was therefore decided to completely rebuild the Tier-1 network with a Spine / Leaf architecture. This paper describes the network requirements and design decision that went into building the new Tier-1 network. It also includes a cost analysis, to understand if the ever increasing network requirements are deliverable in a continued flat cash environment and what limitations or opportunities this may place on future data lakes.

Alan Astbury. 27 November 1934—21 July 2014

Alan Astbury worked in the area of accelerator based subatomic physics. Increasing beam energies, intensities and types of available accelerated beams opened scientific windows to new phenomena throughout his career. Exploiting these new beams required new techniques and the use of the latest technology. Alan was always at the forefront of putting these components together into the experiments needed to confirm or reject the latest theoretical advances or clarify conflicting experimental observations. Following his PhD using the synchrocyclotron at the University of Liverpool and a postdoctoral position at Berkeley, he became a staff member at the Rutherford Appleton Laboratory, where he played a central role in the successive experiments with the Nimrod proton synchrotron, the 26 GeV proton synchrotron at CERN and, perhaps most significantly, with the UA1 experiment at CERN that discovered the W and Z particles. Alan moved to Canada in 1983 and made enormous contributions to Canadian science. He was instrumental in building relationships between Canadian scientists and CERN, DESY and SLAC. As director of the Canadian Institute of Particle Physics and then director of the TRIUMF laboratory, he guided subatomic physics policy and planning for two decades. On the international scene, he was president of the International Union of Pure and Applied Physics.

Muons at ISIS

For the last 30 years, muon experiments at ISIS pulsed neutron and muon facility at the Rutherford Appleton Laboratory, Oxfordshire have been making a significant contribution to a number of scientific fields. The muon facilities at ISIS consist of eight experimental areas. The European Commission Muon facility consists of three experimental areas with a fixed momentum (28 MeV c −1 ). The RIKEN-RAL facility has a variable momentum (17–90 MeV c −1 ) and a choice of negative or positive muons delivering muons to four experimental areas. There is also an area recently used for a muon ionization cooling experiment. In this paper, the ISIS pulsed muon facilities are reviewed, including the beam characteristics that could be useful for muography experiments. This article is part of the Theo Murphy meeting issue ‘Cosmic-ray muography’.

Global height-resolved methane retrievals from the Infrared Atmospheric Sounding Interferometer (IASI) on MetOp

This paper describes the global height-resolved methane (CH4) retrieval scheme for the Infrared Atmospheric Sounding Interferometer (IASI) on MetOp, developed at the Rutherford Appleton Laboratory (RAL). The scheme precisely fits measured spectra in the 7.9 micron region to allow information to be retrieved on two independent layers centred in the upper and lower troposphere. It also uses nitrous oxide (N2O) spectral features in the same spectral interval to directly retrieve effective cloud parameters to mitigate errors in retrieved methane due to residual cloud and other geophysical variables. The scheme has been applied to analyse IASI measurements between 2007 and 2015. Results are compared to model fields from the MACC greenhouse gas inversion and independent measurements from satellite (GOSAT), airborne (HIPPO) and ground (TCCON) sensors. The estimated error on methane mixing ratio in the lower- and upper-tropospheric layers ranges from 20 to 100 and from 30 to 40 ppbv, respectively, and error on the derived column-average ranges from 20 to 40 ppbv. Vertical sensitivity extends through the lower troposphere, though it decreases near to the surface. Systematic differences with the other datasets are typically < 10 ppbv regionally and < 5 ppbv globally. In the Southern Hemisphere, a bias of around 20 ppbv is found with respect to MACC, which is not explained by vertical sensitivity or found in comparison of IASI to TCCON. Comparisons to HIPPO and MACC support the assertion that two layers can be independently retrieved and provide confirmation that the estimated random errors on the column- and layer-averaged amounts are realistic. The data have been made publically available via the Centre for Environmental Data Analysis (CEDA) data archive (Siddans, 2016).

Global height-resolved methane retrievals from the Infrared Atmospheric Sounding Interferometer (IASI) on MetOp

This paper describes the global height-resolved methane (CH4) retrieval scheme for the Infrared Atmospheric Sounding Interferometer (IASI) on MetOp, developed at the Rutherford Appleton Laboratory (RAL). The scheme is novel in: (a) precisely fitting measured spectra in the 7.9 micron region to allow information to be retrieved on two independent layers centred in the upper and lower troposphere and (b) making specific use of nitrous oxide (N2O) spectral features in the same spectral interval to directly retrieve effective cloud parameters to mitigate errors in retrieved methane due to residual cloud and other geophysical variables. The scheme has been applied to analyse IASI measurements between 2007 and 2015. Results are compared to model fields from the MACC greenhouse gas inversion and independent measurements from satellite (GOSAT), airborne (HIPPO) and ground (TCCON) sensors. The scheme is shown to be capable of retrieving column average methane with random errors of ~20–40 ppbv on individual soundings. Systematic differences with the other datasets are typically

Tropospheric ozone and ozone profiles retrieved from GOME-2 and their validation

This paper describes and assesses the performance of the RAL (Rutherford Appleton Laboratory) ozone profile retrieval scheme for the Global Ozone Monitoring Experiment 2 (GOME-2) with a focus on tropospheric ozone. Developments to the scheme since its application to GOME-1 measurements are outlined. These include the approaches developed to account sufficiently for UV radiometric degradation in the Hartley band and for inadequacies in knowledge of instrumental parameters in the Huggins bands to achieve the high-precision spectral fit required to extract information on tropospheric ozone. The assessment includes a validation against ozonesondes (sondes) sampled worldwide over 2 years (2007–2008). Standard deviations of the ensemble with respect to the sondes are considerably lower for the retrieved profiles than for the a priori, with the exception of the lowest subcolumn. Once retrieval vertical smoothing (averaging kernels) has been applied to the sonde profiles there is a retrieval bias of 6% (1.5 DU) in the lower troposphere, with smaller biases in the subcolumns above. The bias in the troposphere varies with latitude. The retrieval underestimates lower tropospheric ozone in the Southern Hemisphere (SH) (15–20% or ~ 1–3 DU) and overestimates it in the Northern Hemisphere (NH) (10% or 2 DU). The ability of the retrieval to reflect the geographical distribution of lower tropospheric ozone, globally (rather than just ozonesonde launch sites) is demonstrated by comparison with the chemistry transport model TOMCAT. For a monthly mean of cloud-cleared GOME-2 pixels, a correlation of 0.66 is found between the retrieval and TOMCAT sampled accordingly, with a bias of 0.7 Dobson Units. GOME-2 estimates higher concentrations in NH pollution centres but lower ozone in the Southern Ocean and South Pacific, which is consistent with the comparison to ozonesondes.

Target fabrication for the POLAR experiment on the Orion laser facility

This article describes the fabrication of a suite of laser targets by the Target Fabrication group in the Central Laser Facility (CLF), STFC Rutherford Appleton Laboratory for the first academic-access experiment on the Orion laser facility (Hopps et al., Appl. Opt. 52, 3597–3601 (2013)) at Atomic Weapons Establishment (AWE). This experiment, part of the POLAR project (Falize et al., Astrophys. Space Sci. 336, 81–85 (2011); Busschaert et al., New J. Phys. 15, 035020 (2013)), studied conditions relevant to the radiation-hydrodynamic processes occurring in a remarkable class of astrophysical star systems known as magnetic cataclysmic variables. A large number of complex fabrication technologies and research and development activities were required to field a total of 80 high-specification targets. Target design and fabrication procedures are described and initial alignment and characterization data are discussed.