The Proton Synchrotron Booster (PSB)

Introduction

The Proton Synchrotron Booster (PSB) is the first synchrotron accelerator in the LHC injector chain, and is made up of four superimposed rings with a circumference of ~157m each. It delivers a variety of beams to the Proton Synchrotron (PS), Super Proton Synchrotron (SPS) and Large Hadron Collider (LHC), and also to fixed target experiments like the ISOLDE facility.

Negative hydrogen ions (H^–: hydrogen atom consisting of an extra electron) are injected from the Linac4 at 160 MeV. At injection in the PSB they go through a stripping foil; stripping (removing) the electrons, so that only the protons are accelerated.

For injection in the Proton Synchrotron (PS), the protons are accelerated to 2.0 GeV, while the ISOLDE facility receives protons at 1.4 or 1.8 Gev.

Did you know? The circumference of the four rings in the PSB corresponds to the circumference of the PS: 4 rings x 157m = 628m!

History

When the PS started running in 1959, the protons were injected directly from Linac1 at 50 MeV and accelerated to 26 GeV. Due to the low injection energy, it limited the number of protons the PS could accept, and thus the PSB was born. The Booster reached the nominal extraction energy on May 26th 1972, and allowed the PS to accept over 100 times more protons than with the Linac1, which greatly increased the beams use for experiments. From 1978 to 2018, the PSB received protons from Linac2 at 50 MeV and accelerated them to 1.4 GeV for injection to the PS.

Due to the goal of higher luminosity (more protons per beam, simply put) in the LHC, a new linear accelerator were built to replace the Linac2: Linac4. Linac4 were inaugurated in 2017, and connected to the PSB during the Long Shutdown from 2019-2021, and has been in operation since.

(If you wonder why it went from Linac2 directly to Linac4: Linac3 is the first injector in the ion accelerator chain, and feeds LEIR – Low Energy Ion Ring.)

Sections

The Proton Synchrotron Booster has the following sections:

• Injection (BI)
• Booster ring, sections 1-16 (BR)
• Ejection (BE)
• Transfer line (BT, BTM, BTY, BTP)