Table of Contents. Check the LCLS Project website to verify 2 of 12 that this is the correct version prior to use.

Transcription

1

2 Table of Contents Summary...3 Mechanical Design Specifications...3 Vacuum...3 Materials...5 Support Requirements...5 Cabling...6 Light Path...6 BLM Synchrotron Radiation Assembly (BL11)...7 Other Requirements...9 BLM Wakefield Radiation Assembly (BL12) of 12 that this is the correct version prior to use.

3 Summary This engineering specification defines the mechanical requirements for the Bunch Length Monitor in the BC1 out area down beam of the first chicane. This instrument consists of two pieces; a synchrotron radiation detector (BL11) for frequencies above 300 GHz and a wakefield detector (BL12) for frequencies below 300 GHz. The synchrotron radiation detector uses an in vacuum mirror to reflect the synchrotron radiation up out of the beam line to an off axis mirror that reflects the beam towards the tunnel wall to a detector mounting plate. The wakefield radiation detector has a ceramic gap in the beamline with wave guides located in close proximity to the gap to collect the wakefield radiation and transmit it down the waveguide to the diode detectors. Mechanical Design Specifications Vacuum The BL11 mirror vacuum chamber interfaces upstream with the beam pipe at the end of the chicanes and will be the fixed point relative to the end of the chicane. The BL11 mirror vacuum chamber downstream interfaces with the beam pipe connected to the downstream Linac. See figure 1. Figure 1, BL11 installation 3 of 12 that this is the correct version prior to use.

4 The synchrotron radiation exit port, orthogonal to the beam line, shall be closed off with a Z cut quartz window that will transmit the CSR signal with minimal attenuation or distortion. There shall be a window port opposite the synchrotron radiation exit port for an alignment diode for the alignment of the detector table to the radiation beam, see figure 2. Figure 2, BL11 Vacuum Chamber The ceramic gap for BL12 is a vendor supplied component, see table 1. After delivery a thin coating of Kovar shall be applied to the inner surface of the ceramic for charge bleed off and then the device will be cleaned and baked out to meet the beam line vacuum component requirements. Nom tube Volts Overall length Gap length Flange Size 1 ½ inches 3 Kv 2.71 inches 0.25 inches 2.73 DS Table 1, Ceramic Gap Specifications 4 of 12 that this is the correct version prior to use.

5 Materials Materials in vacuum will be 304L SST or other specifically approved vacuum materials. All materials in vacuum will be Mill certified. Mill certificates will be included with manufacturing travelers during fabrication, assembly, and test. The fabrication travelers and all documentation will be stored in the project data base after device installation. All materials placed in direct line of sight of the beam line shall be capable of withstanding the tunnel radiation environment. Support Requirements The Vacuum chamber shall have a rigid support to the light pipe or plate attached to the light pipe. The BL11 detectors shall be supported on a stand on the vacuum manifold side of the beam line that is designed to support the required lead shielding. There shall be an aluminum tube covering the deflected radiation beam between the vacuum chamber port and the BL11 detector assembly. See figure 3. Figure 3, BL11 assembly 5 of 12 that this is the correct version prior to use.

6 The BL11 detector stand will be mounted to the tunnel wall and the chicane floor stand with a cover that extends out over the off axis mirror on the vacuum chamber. Cabling The BLM requires both control and signal cables from the detector assembly to the control and feedback system using one of the tunnel penetration ports. The following is a list of the required cabling: Item Wires Notes s and lifiers 4 BNC and 1 - Power 2 detectors in system (BL11) Filter flippers (BL11) 14 conductors 2 filter flippers in system 7 conductors each Mirror actuator at beam (BL11) 7 conductors Two position actuator with limit switches Waveguide lifiers (BL12) 10 BNC and 1 - Power 2 pairs of diode detector & amps plus one Pyro detector and amp Light Path The radiation light path for BL11 is defined in figure 4 and 5. Figure 4 BL11 Light path elevation 6 of 12 that this is the correct version prior to use.

7 Focal Point " " Filter Focal Point Filter " " " " " Off Axis Parabola Beam Splitter Figure 5, BL11 table Top View Beam From Off Axis Parabola on Vacuum chamber The distance between the off axis mirror on the top of the vacuum chamber and the off axis mirror on the detector table shall be approximately 400 mm. BLM Synchrotron Radiation Assembly (BL11) The BLM assembly shall consist of a standard small optical table with a custom stainless steel cover housing the RF optics and detectors. The optics path consists of a focusing/turning mirror, a splitter to illuminate two detectors with a filter flipper holding band pass filters in front of each detector. See Figure 6. 7 of 12 that this is the correct version prior to use.

8 Figure 6, BL11 Plate The stainless steel cover shall have provisions for all the needed electrical penetrations, see cabling section, as well as a port for dry nitrogen purging. The optical table shall mount to the support stand such that proper alignment with the radiation beam from the first off axis mirror on top of the vacuum chamber can be achieved. The BLM detector assembly shall be removable with minimal effort if needed. See figure 7 for the schematic layout. 8 of 12 that this is the correct version prior to use.

9 Signal/Power Dist. Box DC PWR Coax PYRO #1 Coax PYRO #2 Coax - Spare Coax - Spare (2 conductors) (2 conductors) (3 conductors) (2 conductors) To: PYRO s Pyro Flipper Filter Electric Solenoid Limit SW2 OUT (2 conductors) (3 conductors) Beam Line Device Location Limit SW1 OUT Pneumatic Solenoid Limit SW2 IN BLM11 IN Limit SW1 IN Limit SW1 Alignment Table Splitter Mirror Manual Adjust Air Pyro Flipper Filter B E A M Electric Solenoid Limit SW2 O UT (3 conductors) (2 conductors) (2 conductors) Figure 7, BLM Layout Other Requirements The detector assembly shall be under dry nitrogen purge. The mirror for deflecting the synchrotron radiation that diverges from the beam line will be attached to an actuator for complete withdrawal from the beam line. The mirror surface shall be gold coated and capable of reflecting visible light. See figure 8. 9 of 12 that this is the correct version prior to use.

10 Figure 8, BL11 Vacuum Chamber with Mirror in Default position BLM Wakefield Radiation Assembly (BL12) The BLM Wakefield radiation detector is located prior to the first wire scanner in the BC1 out section (21-2) as far from the chicane bend magnet as possible. The ceramic gap for detection of the Wakefield radiation will be a vendor item with a 0.25 inch long ceramic gap. There will be 4 pairs of wave guides and detectors positioned around the gap mounted to an aluminum plate. The plate and wave guides will be aligned to the beam to +/- 1 mm. See figure 9 for schematic layout and figure 10 for installation drawing. 10 of 12 that this is the correct version prior to use.

11 Patch Panel High Quality Coax PWR Figure 9, BL12 Layout 11 of 12 that this is the correct version prior to use.

12 Figure 10, BL12 installation 12 of 12 that this is the correct version prior to use.