FACET Experimental Area
FACET is an experimental facility that provides short, intense pulses
of high-energy electrons and positrons. Nominal FACET beam parameters
are given in Table 1. The facility uses the first two-thirds (Sectors 0
through Sector 20) of the SLAC linac to deliver these beams to an
experimental area with the following elements.
Table 1: Nominal FACET Beam Parameters
| Beam Energy |
20 GeV |
| Particle type |
electrons or positrons |
| Charge per pulse, nominal |
3 nC (~2x1010 e- or e+) per pulse |
| Bunch Length at the Focal Point (σz) |
20µm |
| Transverse Spot size at the Focal Point (σx = σy) |
20µm |
| Nominal Repetition Rate |
1 - 30 Hz |
Physical space:
- The focal point (IP) is nominally 2m downstream of the final
final focus quadrupole but can be shifted using magnet configurations
tailored to the experiment’s needs. The area around the IP, as well as
the beam dump and CTR locations, will have optical table for users to
mount experimental hardware. Each table will have a clear volume
defined by the table surface area extending upwards approximately 4 feet.
Diagnostics :
- Toroids to measure single bunch charge before and after the IP.
- Beam Position Monitors (BPMs) to measure beam orbit
- Profile monitors to measure the beam transverse distribution before and after the IP
- Transverse emittance at the IP (average measurement)
- Energy and energy spectrum before and after the IP
- Bunch length from a transverse deflecting cavity. Relative
bunch length shot-to-shot with average absolute bunch length also
available.
Controls:
- Beam synchronous acquisition
- Camera support. Facilities for users to implement image acquisition for supplied diagnostics in a timely and cost effective manner.
- Gated Analog to Digital Converters (GADCs) with independent triggers per channel.
- Timing. Coarse timing adjustable by increments of 10ns or better, fine timing steps of ~25ps or better, both with less than 25ps jitter.
- Stepper motor support. Facilities for users to implement stepper motor control for supplied diagnostics in a timely and cost effective manner.
Infrastructure:
- 120VAC electrical service distributed in numerous individual receptacles/outlets in and around the IP.
- Air. >80psi air supply for pneumatic actuators. Manifolds for 1/4” tubing connections at the IP and in the vicinity of the beam dump.
- Cooling water
- Vacuum
- Networking. Wired GB Ethernet with taps at IP and near the beam dump. Wireless 802.11n throughout the experimental area.
- Laser PPS system to allow experimenters to install and operate (with appropriate training, PPE etc) lasers rated Class IIIb or higher.
- Rack space. Modest rack space available near the IP, beam dump
and CTR locations plus rack space available outside of the tunnel.
- Cable trays. Cable trays for general purpose signal cable routing from the CTR location to the IP, the IP to the beam dump area, the IP to the penetration to the Klystron gallery and from the Klystron gallery to the user support building.
- Building. Building with >500 ft2 of floor space, GB Ethernet, 802.11n wireless networking and 120VAC electrical service.
- Signal cables.
- General purpose 50 ohm cables routed from the IP to the user support building, from the IP to the beam dump area, and from the IP to the CTR area.
Access:
- Experimenters should be able to access the tunnel within roughly 60 minutes of contacting the main control center (MCC).
- A stairway in sector 19 provides easy access from the sector 20 user support building to the experimental area.
- Access to the SLAC site and FACET facility requires each user to be trained in SLAC safety policies and procedures.
