Hot-water liquid cooling is a key technology in future green supercomputers as it maximizes the cooling efficiency and energy reuse. However the cooling system still is responsible for a significant percentage of modern HPC power consumption. Standard design of liquid-cooling control relies on rules based on worst-case scenarios, or on CFD simulation of portion of the entire system, which cannot account for all the real supercomputer working conditions (workload and ambient temperature). In this work we first introduce an analytical model, based on lumped parameters, which can effectively describe the cooling components and dynamics, and can be used for analysis and control purposes. We then use it to design an energy-optimal control strategy which is capable to minimize the pump and chiller power consumption while, meeting the supercomputer cooling requirements. We validate the method with simulation tests, taking data from a real HPC cooling mechanism, and comparing the results with state-of-the-art commercial cooling system control strategies.

Energy-aware cooling for hot-water cooled supercomputers

To assist the beam commissioning in the Spallation Neutron Source (SNS) linac, a general purpose Radio Frequency (RF) tuning application has been written to help set RF phase and amplitude. The method involves varying an Rf cavity amplitude and phase settings over a fairly large range and comparing the measured downstream beam phase response “signatures” to model predictions. The model input for cavity phase, cavity amplitude, and the beam energy are varied to best match observations. This scheme has advantages over other RF tuning techniques of not requiring intercepting devices (e.g. Faraday Cups), and not being restricted to a small linear response regime near the design values. The application developed here is general and can be applied to different RF structure types in the SNS linac. Example application for the SNS Drift Tube Linac (DTL) and Coupled Cavity Linac (CCL) structures will be shown

Pasta &#8211; an RF Phase Scan and Tuning Application

The Spallation Neutron Source (SNS) accelerator delivers a one mega-Watt beam to a mercury target to produce neutrons used for neutron scattering materials research. It delivers ~ 1 GeV protons in short (< 1 us) pulses at 60 Hz. At an average power of ~ one mega-Watt, it is the highest-powered pulsed proton accelerator. The accelerator includes the first use of superconducting RF acceleration for a pulsed protons at this energy. The storage ring used to create the short time structure has record peak particle per pulse intensity. Beam commissioning took place in a staged manner during the construction phase of SNS. After the construction, neutron production operations began within a few months, and one mega-Watt operation was achieved within three years. The methods used to commission the beam and the experiences during initial operation are discussed.

/pdf/the-spallation-neutron-source-beam-commissioning-and-initial-cgnpsl3uu1.pdf

The Spallation Neutron Source Beam Commissioning and Initial Operations

The Spallation Neutron Source (SNS) [1] has been recently commissioned. Strategies for the initial beam commissioning of the linac and storage ring will be discussed. The superconducting linac (SCL) commissioning posed unique challenges, in particular accommodating an unanticipated wide range of cavity performance. Methods for setting cavity phases and determination of amplitudes will be discussed. The ring commissioning involved the usual establishment of a circulating beam, and then measurement and correction the tune and beta functions, all with a low intensity beam. Then the gradual increase of beam intensity and phase space painting were investigated. The methods to accomplish these tasks will be discussed. Key factors in the successful commissioning were flexibility in accommodating beam conditions that are different from the design, model based applications, good communication between the different groups, and prebeam testing.

Sns commissioning strategies and tuning algorithms

Theoretical modeling by means of Matlab Simulink program and experimental investigation of heat processes in the INR Linac drift tube tanks allow studying influence of these processes at the tank resonance frequency and creating of the frequency control system model. At that, the main attention is paid to accordance of modeling results and processes in the real systems. In turn, creation of control frequency system model gives a possibility to optimize the structure and parameters of the control system, stabilizing tank resonance frequency, and increase the accelerator operation efficiency.

https://epaper.kek.jp/r06/papers/modp27.pdf

Simulation of the inr ras dtl frequency stabilization system

The Δt procedure is a time of flight technique for setting the phases and amplitudes of accelerating fields in a multi-cavity linac. It was initially proposed and developed for the LAMPF linac in the early seventies [1,2] and since then has been used in several accelerators [3,4]. The SNS linac includes four CCL modules (Side Coupled Structure) operating at 805 MHz for the energy range from 86.8 MeV up to 185.6 MeV. The Δt procedure has been implemented for the SNS CCL linac and was used for initial beam commissioning of three CCL modules. A brief theory of the procedure, the results of the design parameter calculations and the experimental results of phase and amplitude set points are presented and discussed.

Development and Implementation of &#948;T Procedure for the SNS Linac

The Resonance Control Cooling System (RCCS) was designed by Los Alamos National Laboratory for the warm linac of the Spallation Neutron Source. The primary design focus was directed on water-cooling of individual component contributions. The sizing of the RCCS water skid was accomplished by means of a specially created SINDA/FLUINT model tailored to these system requirements. A new model was developed in Matlab Simulink and incorporates actual operational values and control valve interactions. The model took into consideration the dependence of RF input power on cavity detuning values during transients, time delays that resulted from water flows through the heat exchanger, the dynamic process of water warm-up in the cooling system due to dissipated RF power on the cavity surface, differing contributions on the cavity detuning due to drift tube and wall heating, and a dynamic model of the heat exchanger with characteristics, which were in close agreement to the real unit. Because of the Matlab Simulink model, investigation of a wide range of operating issues during both transient and steady state operation is now possible. Some results of the DTL RCCS modeling are presented.

Spallation Neutron Source Drift Tube Linac Resonance Control Cooling System Modeling

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Development and Implementation of δT Procedure for the SNS Linac

Spallation Neutron Source Drift Tube Linac Resonance Control Cooling System Modeling

Yu. Kiselev

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Development and Implementation of &#948;T Procedure for the SNS Linac

Spallation Neutron Source Drift Tube Linac Resonance Control Cooling System Modeling

Development and Implementation of δT Procedure for the SNS Linac