LEP pre-injector

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The building of the LEP Injector Linac (LIL), which then housed the CLIC Test Facility. The green LIL logo can be seen on the left in the picture.

The LEP Pre-Injector (LPI) was the starting point for electrons and positrons in the accelerator complex for the Large Electron-Positron Collider (LEP), which was in operation at CERN from 1989 to 2000 . The system included the LEP Injector Linac (LIL), consisting of LIL V and LIL W, as well as the Electron Positron Accumulator (EPA).

history

The groundbreaking for the Large Electron-Positron Collider took place in September 1983, the design for its injection infrastructure, i.e. for the LEP Pre-Injector (LPI), was not completed until 1984. The preparations and construction were carried out in close partnership with Laboratoire de l'accélérateur linéaire (LAL) in Orsay, France. The experience and expertise of the LAL was of particular importance for the design, as no electron / positron accelerators had been in operation at CERN before this point in time.

The first electron beam with an energy of 80 keV was produced on May 23, 1985. From July 1986, LIL injected electrons with an energy of 500 MeV into the Electron Positron Accumulator for the first time, shortly afterwards it reached the desired intensity for electrons. The same was achieved for positrons in April 1987.

In the following years, the accelerator system was put into operation, tested and optimized. The electron and positron beams were threaded step by step through the various accelerator systems: After LIL and EPA, the proton synchrotron (PS) and the super proton synchrotron (SPS) followed, whereupon the particles finally reached the LEP ring. This was successfully carried out for the first time on July 14, 1989 - one day earlier than originally planned. On August 13, the particles were brought to collide for the first time and on September 20, the first experiments at the LEP began to record data from the collisions.

From 1989 until the decommissioning of the Large Electron-Positron Collider on November 7, 2000, the LPI acted as its electron and positron source. In addition, the LPI was operated for other experiments (see section below) until April 2001. Shortly afterwards, the LPI was converted into CLIC Test Facility 3 (CTF3). Preparatory tests and experiments for the future Compact Linear Collider (CLIC) were carried out there until the end of 2016 . From 2017 the system was converted to the CERN Linear Electron Accelerator for Research (CLEAR).

business

  • LEP Injector Linac (LIL)

  • LIL W and the
    electron-positron converter

  • Electron Positron Accumulator (EPA)

The LPI consisted of the LEP Injector Linac (LIL), which in turn comprised the two parts LIL V and LIL W, and the Electron Positron Accumulator (EPA).

LIL was formed from two linear accelerators , which were arranged one behind the other in tandem, and had a length of about 100 meters. At the starting point of the facility, in LIL V, electrons with an energy of 80 keV were generated using a hot cathode . LIL V then accelerated high currents of these electrons to an energy of around 200 MeV. These were either accelerated further or used to generate positrons . At the beginning of LIL W, directly following LIL V, the electrons were shot at a tungsten target , creating positrons. Subsequently, both electrons and positrons could be accelerated to 500 MeV in LIL W. Initially the plan was to achieve energies of up to 600 MeV with LIL W. In the course of the first few months, however, it turned out that 500 MeV was sufficient and could guarantee significantly more stable operation.

LIL consisted of so-called S-band linacs , which accelerated electrons and positrons. This linear accelerator used cavity resonators which by a pulsed 35 MW - klystron at a frequency of 3  GHz were fed.

After the particles passed through LIL, they were placed in the EPA; there the electrons circulated clockwise and the positrons counterclockwise. Both types of particles were collected at the EPA in order to achieve sufficient beam intensity and to match the high frequency of the LIL (100 Hz) to that of the PS (around 0.8 Hz). After passing through the EPA, the particles were delivered to the PS and SPS for further acceleration before reaching their final destination, the LEP ring.

The circumference of the EPA was 125.7 meters, which was exactly one fifth of the circumference of the PS.

Other experiments

The electrons and positrons provided by the LPI were not only used by the LEP, but also by other experiments and test setups that were directly connected to the LPI building.

The first experiment of this kind was the Hippodrome Single Electron (HSE) experiment. The L3 collaboration commissioned the production of individual electrons in March 1988. At the end of 1988 the set-up was in operation and was used for the precise calibration of the L3 detector, which was to be installed shortly afterwards as one of the four LEP experiments.

Those particles that were not directed into the EPA from LIL were directed straight into the LIL Experimental Area (LEA). The electrons arriving there have been used for many different applications over the years, but mainly for testing and preparing the detectors of the LEP and later the LHC . For example, the preparations for the LHC were in 2001 in the course of optical fibers in one of the CMS - calorimeter tested.

In addition, the two Synchrotron Light Facilities SLF 92 and SLF 42 used the synchrotron radiation , which was emitted by the electrons circling in the EPA. Until the beginning of 2001, the COLDEX experiment at SLF 92 investigated the effects of synchrotron radiation on the vacuum chambers of the LHC. SLF 42 was used for research on getter strips , which were prepared for use in the vacuum chambers of the LHC.

The last experimental success of the LPI was the PARRNe experiment: The electrons from the LPI generated gamma rays , which were used to produce neutron-rich radioactive krypton and xenon atoms.

Web links

Commons : LEP Pre-Injector  - collection of images, videos and audio files

Individual evidence

  1. ^ A b D. J. Warner: New and Proposed Linacs at CERN: The LEP (e + / e-) Injector and the SPS Heavy Ion (Pb) Injector (1988) . Retrieved July 24, 2018
  2. ↑ CERN bulletin n ° 24 (1985) . Retrieved July 30, 2018
  3. ^ S. Myers: The LEP Collider, from design to approval and commissioning (1990) . Retrieved July 30, 2018
  4. ↑ a b c d CERN Bulletin 20/2001: LPI goes out on a high note . Retrieved July 31, 2018
  5. ↑ G. Geschonke and A. Ghigo (editors): CTF3 Design Report (2002) . Retrieved July 31, 2018
  6. ↑ Official CLEAR Homepage . Retrieved July 31, 2018
  7. ↑ a b c G. McMonagle et al .: The Long-Term Performance of the S-Band Klystron Modulator System in the CERN LEP Pre-Injector (2000) . Retrieved July 30, 2018
  8. ^ F. Dupont: Status of the LEP (e + / e-) Injector Linacs (1984) . Retrieved July 30, 2018
  9. ↑ S Gilardoni, D. Mangluki: . Fifty years of the CERN proton synchrotron Vol II (2013) . Retrieved July 10, 2018
  10. ↑ B. Frammery et al .: Single Electron Beams from the LEP Pre-Injector (1989) . Retrieved July 31, 2018
  11. ↑ V. Baglin et al .: synchrotron radiation studies of the LHC dipole beam screen with COLDEX (2002) . Retrieved July 31, 2018
  12. ↑ S. Essabaa et al .: The study of a new PARRNe experimental area using an electron linac close to the Orsay tandem (2002) . Retrieved July 31, 2018