Scavenger Extraction Karen Goldsmith Shawn Alverson
Topics Beam line and area maps High Power Target (HPT) How to establish first beam to HPT Setting energy (configs, multiknobs, Fast Phase Shifters, etc.) Setting up the kicker/dc Extraction PR185 Bend region General Tune-Up Phase Scans MPS HLAM MTLM (TIU) BCS References
Beam Line Overview Relocated from target for use in DC Extraction Energy diagnostic region Gunbarrel Collimator Same BPM with different BPMP with offsets for either line HBENDs all on one string (LGPS 3)
Tantalum/Tungsten Target Material: 90% Tantalum, 10% Tungsten Target mounted on cam which rotates the target relative to the beam incident position Keeps target from overheating Motor interlocked into TIU Machine Protection System
Positron Vault PPS information may not be accurate. PPS stopper permit enable box X2183 Positron vault local PPS panel BSOPOS01 (X) µ R Positron vault PPS door (PVN1 door) Portal blocks and PVN1A control box and status box Shielding block EO 3 EO Positron vault PPS gate (PVN1A gate) Portal blocks Positron vault Portal blocks and PVN1A emergency exit control box East turn around Rask hazard enable box Beamline EO 2 EO Positron target block EO 1 EO P R Equipment shaft Radiation gate reset (X) Radiation gate (X) Radiation gate alcove Linac concrete rolling blocks
Establishing First Beam Steps for establishing first beam into the scavenger extraction line: 1 Setup Septa/Bend strength for desired energy 1 Setup Septa/Bend strength for desired energy 2 Setup kicker strength/timing or DC extraction 3 Adjust Sec. 17/18 energy to match bends 4 Fix energy spread using Phase Ramp 5 Clean up steering as needed based on gold reference orbit
E+ Tune-Up Panel This panel contains links to the most common tuning devices for the scavand e+ lines. Location: OPERAT_MAINT => E+ Tune-up and Rate OR E+ SYSTEM => Tune-up and Rate
Setting Up the Bend Energy Load EXT Magnet and Timing Configs!
HLAM In addition to ensuring that the HLAM EMI is turned on, you must also verify that it has been put IN to affect the beam. HLAM Status HLAM In/Out Controls
Setting Up the Bend Energy cont. Multiknobs Create knob to scale from configfile Use Scav Energy multiknobs Absolute knobs scale all magnets from design with respect to HBENDs DANGEROUS! Used for large energy changes but you will probably have to manually adjust the septa afterwards to re-match into the quad lattice Relative knob scales all extraction line magnets (bends, septa, quads, and LI19 XCOR 700) uniformly from current value Knob adjusts bend energy by ~0.5 GeV/turn Generally better to use this knob than the absolute to avoid getting lost Magnet Scaling factors: HBEND BDES = SCAV Energy * 1.6753 VBEND BDES = SCAV Energy * 0.79749 HLAM BDES = SCAV Energy * 0.61222 VLAM BDES = SCAV Energy * 0.270234
Setting Up the Bend Energy cont. Positron Multi-Knob Panel Location: Multi_Device_Knobs => POSITN_KNOB_INDEX Absolute Knobs OR E+_TUNEUP_&_RATE => POSITN_KNOB_INDEX Relative Knob
Setting Up the Kicker Make sure kicker current scope looks correct Scope is on channel 3-20 Scope signal should look similar to this.
Setting Up the Kicker Kicker timing should be close after loading TIMEPOS timing config. If small adjustments are needed, use Fine Multiknob (kicker timing panel) You can also use the Raw signal, but you must Freeze timing feedback before adjusting, put back to Track when done To turn the kicker on safely we must use a macro to slowly ramp up the charge for the thyratron PFN.
Setting Up the Kicker Setting the kicker energy: Send beam down to Sector 19 and make sure orbit is generally flat Incoming orbit must be flat in order to reduce unintentional angle into extraction line to insure proper kicker and energy setup Turn on kicker and adjust BDES (actually voltage) to deflect beam by about -7 mm in y on PR171 or LI19 BPMS701 Y EP01BPMS 170 = LI19BPMS 701 + Offset May need to tweak VLAM negative to get beam fully into the extraction line.
No EP01 Kicker? If EP01 Kicker is not functioning, it is possible to use DC Extraction to send beam into the Scav Extraction Line. Use LI19 YCOR 503 to steer -7 mm on PR171 or LI19 BPMS 701 Y If not enough room on YCOR 503, you can also use EP01 YCORs 145 and 146 (used to be 282)
Setting Up Extraction Energy Scavenger beam typically set to extract between around 20-25 GeV(FACET = 23 GeV) Once beam is deflected into extraction line, adjust Sector 17/18 energy to maximize signal on EP01 TORO 175 and attempt to see beam on PR185 Can make coarse energy adjustment by adding/dropping tubes upstream of Sec. 17/18 Fine energy adjustments made by moving 17/18 PAU fast phase shifters (17_18_FFPHAS off Tune-Up Panel)
PR185 Once the beam is on PR185 you can now fine tune energy and energy spread and turn on EP01_SCAV_LOOP energy feedback Feedback uses BPM 186 for state measurement Use Phase Ramp (DR12 PHAS 61) to minimize energy spread on PR185
PR185 cont. High Energy is up and to the left, Low Energy is down and to the right. Energy spread can streak the beam wider than the up stream collimator aperture. Adjust phase ramp to ensure that the whole beam is visible and on energy.
Gun-Barrel Collimator After PR185, a cylindrical collimator was installed to protect from high power off-energy beams. It is aligned such that the aperture should only accept on energy beams into the bend region Use EP01 TORO 199 to verify that the beam has passed through the collimator If little or no beam on TORO 199: Make sure that the Pos. Vault PPS Stoppers are removed Maximize throughput by adjusting 17/18 fast phase It should not be necessary to move the collimator
Bend Region Once past Toroid 199, the beam enters the vertical and horizontal bend region. Beam should be on energy now so it should make it through the bends with a little help from the correctors to steer the orbit on BPMs. -XCORs are trim windings on the bends -YCORs are trim windings on the quads Bends are rolled through the extraction line! -Mostly bend in X but do have a small Y contribution
High Power Target In order to steer on the target use: For X: EP01 XCOR 265 and 275 For Y: EP01 YCOR 270 and 280 Diagnostics: PR390 (EP02 Fixed Target) EP01 TORO 375 and PT01 TORO 376
General Tune-Up Phase drift Where: Energy spread changes on PR185 What to do: Check upstream throughput, may need to tweak Phase Ramp (DR12 PHAS 61) If Sec. 10 chicane is ON may need to adjust Sec. 2-9 and Sec. 10-19 SBST phases separately to fix Energy drift Where: Beam position shift on PR185 and EP01 BPMs 186 What to do: ScavFeedback should auto-correct, may need to adjust 17/18 Fast Phase or add/drop klystron if change is large
Phase Scans The scavenger extraction line can and will be used as the primary dispersion region for phasing klystrons. Y Use energy BPM EP01 186 for correlation plot Rough scans can be done using PR185 Two methods exist for scanning tubes upstream of 19-6 (except for Sec. 17 and 18 which are special) BPMS EP01 185 X (ELECEP01) 1.0 0.5 0.0-0.5-1.0-1.5-2.0-2.5 = A * (X - B)**2 + C A = 9.0421E-04 STD DEV = 6.3609E-06 B = 119.7 STD DEV = 0.1276 C = -2.058 STD DEV = 3.4889E-03 RMS FIT ERROR = 5.3587E-02 Chi-square/DOF = 6.071 * * * * * * * * * * * * * * * 110 130 150 170 SBST LI17 1 KPHR (S-17-1) SBST LI17 1 KPHR STEPS=41;3 MIN=93.668 MAX=173.67 * * * * * * *
Phase Scans cont. Phase Scan methods: 1 Move KLYS/SBST KPHR with SCAV energy feedback OFF and look for max energy For BPM 186, Emax= Xmin For PR185, Emax= Up and to the Left 2 Scan KLYS/SBST KPHR with SCAV energy feedback ON and look at feedback actuator Emax = minimum feedback contribution Use FBCK EP01SCAV ENGYSCAV CMND in correlation plot to see feedback contribution
Phase Scans cont. For Sectors 17 and 18: Turn OFF SCAV Energy feedback Put the sector you want to scan on crest by moving the fast phase shifter to 0 You will probably have to drop tubes in order to stay on PR185 Scan KLYS/SBST KPHR in correlation plot on EP01 BPMS 186 like normal Dial back fast phase shifter and add tubes to get back to original complement Turn ON SCAV Energy Feedback
MPS TIU Interlocks 1553 Interlocks HLAM Interlocks
MPS -HLAM Many devices in the Scavenger Extraction Line and Positron Vault are interlocked directly into the HLAM and extraction kicker since these are the primary fast means of inhibiting beam to these areas.
MPS -HLAM HLAM interlocks and reset panels - Allows you to check input states and pull valves (if vacuum looks ok) - EP01 and EP02 contain separate inputs into the HLAM/Kicker shut-off path which can be reset from their respective panels HLAM Permit Reset
MPS (TIU) Most TIU devices will reset the normal way off of the LinacTIU panel - Exception: Moving Target Logic Module chassis
MTLM MPS (TIU) The High Power Target has its own MPS interlocks through the Moving Target Logic Module (MTLM) Module is interlocked through the LinacTIU (Sec. 20) but the TIU input will not reset until the MTLM chassis has been reset itself. MTLM interlock panel Located off Positron Target Control panel Reset the MTLM chassis before the TIU
BCS Positron BCS signals located in Zone 2 of the SCP BCS Panel
References Eric Reuter Mechanical Design and Development of a High Power Target System for the SLC Positron Source, SLAC-PUB-5369 Dec. 1991 Scavenger Extraction Beam Line Map, SLAC-I-040-20200-001-R004 Positron Vault PPS Zone Map, SLAC-I-040-30200-002-R040