DESY Research Centre Research Articles

Colliders of the future

Just over a year ago scientists investigating data from the Large Hadron Collider confirmed the discovery of the Higgs Boson - the holy grail of the Standard Model of particle physics that underpins scientists' understanding of the fundamental workings of our universe. Exactly what sort of collider should come next is a matter of debate. Options for a successor range in size and feasibility, but a central question is what the machine should be colliding. The LHC collides opposing beams of either protons or lead nuclei, which are made up of neutrons. Making a decision about what kind of collider to build depends on what you expect to find. The Higgs Boson was discovered to have a mass of 125GeV (gigaelectronvolts), well within the 1TeV (teraelectronvolt) collision energy scope of proposed lepton colliders. But if new physics beyond the Standard Model such as supersymmetry and string theory exists, as many theorists expect, collision energies beyond the refitted LHC's 14TeV are widely considered essential. The most technologically mature option is the International Linear Collider (ILC) - an electron-positron collider with an initial collision energy of 500GeV and the potential to upgrade to 1TeV. The technology is well established, with a smaller version running at the DESY research centre in Hamburg.

Signal-to-noise measurements on irradiated CMS tracker detector modules in an electron testbeam

The CMS experiment at the Large Hadron Collider at CERN is in the last phase of its construction. The harsh radiation environment at LHC will put strong demands in radiation hardness to the innermost parts of the detector. To assess the performance of irradiated silicon microstrip detector modules, a testbeam was conducted at the Testbeam 22 facility of the DESY research center. The primary objective was the signal-to-noise measurement of fully irradiated CMS Tracker modules to ensure their functionality up to 10 years of LHC operation. The paper briefly summarises the basic setup at the facility and the hardware and software used to collect and analyse the data. Some interesting subsidiary results are shown, which confirm the expected behaviour of the detector with respect to the signal-to-noise performance over the active detector area and for different electron energies. The main focus of the paper are the results of the signal-to-noise over reverse bias voltage measurements for CMS Tracker Modules which were exposed to different radiation doses.

A Distributed System for Radiation Monitoring at Linear Accelerators

This paper discusses a system for an on-line neutron fluence monitoring at linear accelerators. The system consists of a SRAM-based detector and a radiation-tolerant read-out system. The neutron fluence was measured in several locations of the accelerator. Monitoring of the radiation environment in an accelerator tunnel is necessary to assure reliable long-term operation of electronic systems placed in the tunnel. Monitoring of the chamber is especially important during the design stage of a linear accelerator. The new design of 20 GeV linear accelerator X-ray Free Electron Laser (X-FEL) is currently approved for construction at DESY Research Centre in Hamburg , . The presented paper is based on our research and experimental measurement carried out at 1.2 GeV superconducting electron linac driving the Vacuum UltraViolet Free Electron Laser (VUV-FEL). The application of a pair of TLD-700 and TLD-500 or superheated emulsion (bubble) dosimeters enables the supervision of neutron fluence in accelerators . This process requires continuous and arduous calibration of TLDs, therefore this method is not convenient. Moreover, it is impossible to monitor the radiation environment in real-time. The presented system fills the market niche of real-time neutron monitoring for high-energy accelerators. Neutron fluence and gamma dose measured in this way can be used for the detailed analysis of the VUV-FEL or X-FEL environments. Monitoring of the radioactive area in a linear accelerator tunnel could be helpful to the diagnosis and reduction of beam losses. We have conducted experiments with the distributed system dedicated to neutron flux measurement at the DESY Research Centre in Hamburg. The devices were exposed to a neutron field from an Americium-Beryllium (n,alpha) source 241AmBe. The systems were installed in two accelerators: Linac II and VUV-FEL

The application of a SRAM chip as a novel neutron detector

High-density, fast digital devices, like field programmable gate arrays (FPGAs), microcontrollers, and static random access memories (SRAMs), can be produced by nanotechnology. New technologies allow the design of fast and powerful devices; however, the decreasing dimensions create new problems. Even at ground level, cosmic ray particles arriving from outer space can affect digital devices and provoke single-event effects (SEEs) due to the smaller sensitive volume (SV). In general, for decreasing feature size of memory cells the expected critical charge decreases and the expected sensitivity to radiation increases. High-density SRAM chips were used to design a fast response, highly sensitive neutron detector. We have conducted experiments with SRAMs at the DESY Research Centre in Hamburg, Germany. Memory contents (number of SEU) were recorded as a function of neutron expose time. The chips were exposed to a neutron field from an americium-beryllium neutron source (241AmBe). The second experiment was accomplished in the 450 MeV electron Linac (Linac II) tunnel. Another batch of SRAMs was irradiated with 60Co gamma rays to a dose of about 60 Gy, and no SEU was registered. This shows that gamma radiation has no substantial effect on the production of SEU in the SRAM. The proposed detector could be ideal for the detection of pulsed neutron radiation produced by high-energy electron linear accelerators and synchrotron facilities, which are currently in operation and planned for the near future.

Dosimetry of high-energy electron linac produced photoneutrons and the bremsstrahlung gamma-rays using TLD-500 and TLD-700 dosimeter pairs

The neutron and gamma doses are crucial to interpreting the radiation effects in microelectronic devices operating in a high-energy accelerator environment. This report highlights a method for an accurate estimation of photoneutron and the accompanying bremsstrahlung (gamma) doses produced by a 450 MeV electron linear accelerator (linac) operating in pulsed mode. The principle is based on the analysis of thermoluminescence glow-curves of TLD-500 (Aluminium Oxide) and TLD-700 (Lithium Fluoride) dosimeter pairs. The gamma and fast neutron response of the TLD-500 and TLD-700 dosimeter pairs were calibrated with a 60Co (gamma) and a 241Am–Be (α, n) neutron standard-source, respectively. The Kinetic Energy Released in Materials (kerma) conversion factor for photoneutrons was evaluated by folding the neutron kerma (dose) distribution in 7LiF (the main component of the TLD-700 dosimeter) with the energy spectra of the 241Am–Be (α, n) neutrons and electron accelerator produced photoneutrons. The neutron kerma conversion factors for 241Am–Be neutrons and photoneutrons were calculated to be 2.52×10 −3 and 1.37×10 −3 μGy/a.u. respectively. The bremsstrahlung (gamma) dose conversion factor was evaluated to be 7.32×10 −4 μGy/a.u. The above method has been successfully utilised to assess the photoneutron and bremsstrahlung doses from a 450 MeV electron linac operating at DESY Research Centre in Hamburg, Germany.

Meeting Reports: Forty Years with Synchrotron Radiation at DESY

On May 19, 2004, 250 guests from all over the world joined the DESY research center to celebrate 40 years of research with synchrotron radiation at DESY in Hamburg. “The first measurements with the light beam from the DESY ring accelerator started in 1964. DESY was one of the seed laboratories in which the worldwide success story of research with synchrotron radiation began,” Albrecht Wagner, chairman of the DESY Board of Directors, explained in his welcoming address. “Today, more than 1,900 scientists from 31 countries come to DESY every year to carry out experiments with synchrotron radiation.” Forty years ago, synchrotron radiation at DESY started from scratch. At the beginning of the 1960s, the radiation generated by the electrons in the bending magnets of their new 6 GeV electron synchrotron was regarded by DESY particle physicists as an unwanted, disruptive effect.