Advanced Laser Personnel Safety System at Jefferson Lab

Transcription

1 Advanced Laser Personnel Safety System at Jefferson Lab 2012 DOE Laser Safety Officer Workshop Stanford Linear Accelerator Center, Sept Stephen Benson and Kevin Jordan, Newport News VA

2 What is Jefferson Lab? JLab is a world leader in SRF technology: contributing to SNS, 12 GeV Upgrade, and ILC facility Superconducting rf (SRF) technology makes the re-circulating accelerator feasible and meets demanding specs for forefront experimental program Providing ~1200 active international users with a unique electron beam, three experimental halls, and computational, phenomenology and theory support A B C High luminosity, high resolution detectors in Halls A, B, and C

3 Free Electron Laser Facility provides seven User labs for experimental activities

4 General Goals and Philosophies Overall goal is to allow users to do great science but provide them with the safest work experience possible while simultaneously providing as much flexibility at possible. How do we accomplish this? Use engineered controls wherever possible. No defeating interlocks to get something done. Audit systems regularly to make sure system is safe. Use operator staff to continually monitor the state of the system. Provide training to ensure compliance with administrative safeguards. Make the system as user friendly as possible HPI considerations reduce errors Reduces the temptation to violate safety protocols Monitor users constantly Many are used to lack of safety rules

5 Lab Capabilities High power IR µm tuning range. Up to >10 kw power output (narrowband). Up to >300W output (broadband tunable) Emits harmonics throughout the visible High power UV nm accessible tuning range. Up to > 1kW power output (150 W demonstrated to date) THz beam Broadband source mm wavelength band Tens of Watts average power. Conventional lasers (some examples) Medium power Nd:YAG (150 W) 1 khz MOPA Ti:sapphire laser (Titan) Q-switched tripled Nd:YAG (HIPPO) 5 kw carbon dioxide laser Low power mode locked lasers (Tsunami)

6 Special Hazards Associated with the User Labs Very high Power levels s can operate at any wavelength allowed by the beam energy, optics, and wiggler wavelength and strength. s emit coherent harmonics n th odd harmonic is reduced in power by about 10 -n from the fundamental power level. For example:. 10 kw at 1.5 microns. 10 W at 500 nm. 100 mw at 300 nm Picosecond pulse structure User equipment and/or materials Laser byproducts

7 Access States There are four access states (modes) in a user lab: Open Mode Anyone can enter the lab. The lab must drop to Open before changing to another state. Alignment Mode (Local laser,, and HeNe alignment) Users can now be directly exposed to the laser beams. LPE required at all times. limited to 0.5% duty cycle and lower power. Harmonic blocking filter used with IR ND filter used with UV Hutch Mode Can bypass interlocks if all beams are blocked. Allows quick change-out of samples or minor adjustments. Exclusionary Mode No-one allowed in the lab. Must sweep lab before locking up.

8 LPSS Chassis Each lab has the same Laser Personnel Safety System chassis with the same PLC programming. Master LPSS chassis interfaces to the and is located in a room only accessed by Laser Operators. Laser permit indicator is lit when the lab is made up. Key on box switched between Hutch and Exclusionary mode.

9 Access to the labs When a lab is in LASER PERMIT a yellow flashing light is on above the door and the doors are interlocked and maglocked. The state of the lab is indicated by lights on the door. In Exclusionary mode the maglocks cannot be bypassed (exit button crashes the lab). In Hutch and alignment modes the maglocks can be bypassed for up to 15 seconds via an EXIT button or a smart card reader. Color coding on the LPE signs and buttons enhances LPE choices. Magnetic LPE sign Certification magnet Access State Lights LOSP

10 Access controls (cont.) Each lab has a CCTV monitor next to the door to monitor activities in the lab. Button must be pushed during sweep to enable a given laser. Smart card reader is used to start and end a sweep and to gain access to the lab in alignment mode and hutch mode. Access tied to training database. May be able to tie LPE to access as well.

11 Mirror Cassette Assembly Harmonic blocking filter is inserted when delivering alignment mode beam. Hutch bypass shutter is tied to lab shutter. When closed the lab shutter is also closed. High power Lab shutter. Mirror cassette allows beam to pass through in its default position.

12 Typical Key Controls Lab Shutter key Orange box is ANSI standard key for the. Local laser mode locks out the Lab shutter and the mirror cassette. Same key used for Lab Shutter and Local Laser/ mode. Hutch bypass controls all hutch bypass shutters and bypasses hutch interlocks. Hutch interlock bypass switch Local Laser/ key

13 New Capability with Multi-Wavelength Lasers We have developed a system that allows us to match the LPSS permissions to the wavelength of a multiwavelength laser. Proximity switches on laser tell the LPSS what wavelength is available. LPSS gives permission if that wavelength is requested via buttons on the door panel.

14 Administrative Controls Not all controls can be engineered. Users must control beam paths to keep high power beams from hitting un-cooled surfaces. Users must ensure that personnel are cleared from the lab before it goes into Laser Permit. Users must actually put on LPE. They are monitored via CCTV (two strike policy). LPE needs change with the laser setup. Users are responsible for wearing the correct LPE and putting out the correct sign. Untrained personnel not allowed in lab.

15 Summary We have managed to achieve enormous flexibility with a system that is fairly easy to use and is quite safe. Most users learn the system and are comfortable with it within a few days. We link access to training so that unqualified people cannot make up a lab. There are very few administrative controls. Almost everything is engineered controls. Regular audits ensure that the engineered controls work. Well trained operators are also useful to find problems with the system. We have engineered a workable solution to the problem of linking access to the actual laser wavelength for a HIPPO laser.