Progress of Shintake Monitor Work

October 7, 2009 T. Yamanaka

New Laser

Laser Installation

• The new laser was delivered on September 24.

Laser Head Power Supply Box

Laser Installation

• The new laser was put on the current optical table.• The old laser was put on the additional table in the

extended laser hut.

New Laser Old Laser

Laser Setup

• Engineer from laser company– Installation of SHG– Connection of N2 flow line at the laser head

– Filling up of internal cooling water

• Measurement of laser parameter– Power– Profile– Waveform– Timing jitter

Laser Power

• Specification– 2500mJ/pulse @ 1064nm– 1500mJ/pulse @ 532nm

• Measured– 2300mJ/puse @ 1064nm （ with SHG unit ）– 1510mJ/pulse @ 532nm （ S polarization ）– 1360mJ/pulse @ 532nm （ P polarization, at first ）– 1220mJ/pulse @ 532nm （ P polarization, later ）

• Power is reduced by 10-20 % when the polarization is changed at the harmonic generation.

Laser Profile

• Measured the split laser light by CCD camera– Laser was operated with full power.– A focusing lens was used (laser width is large).

S polarization P polarizationMeasured at the laser company(don’t focused)

cf ) old laser

Laser Waveform

• Used a PIN-photodiode and an oscilloscope to see the laser light waveform.

Seeded Unseeded

•　 1 DIV = 5ns•　 Pulse width (FWHM): 8-9 ns with seeded laser

Timing Jitetr

• Measured the time interval of – Q-Switch trigger (internal clock, 6.25 Hz)– laser light （ measured by PIN-photodiode ）

RMS = 258 psGaussian-like distribution

cf ) Old laser

RMS = 409 pshave tail

Issue

• Polarization– There is a way to change the polarization on the

optical table by mirror reflection.

• Pressure of external cooling water is not enough.– Now operate with cancelling the water pressure

interlock– Need to test the cooling power of the chiller

Polarization

Trouble: Damage to SHG

• Operate the laser with us in next week of installation• Bad profile was observed （ get chipped ）• Found damages to SHG when opening the SHG unit• Laser power was bit decreased.

– 1090mJ/pulse @ 532nm （ P polarization ）– 1220mJ/pulse @ 532nm （ S polarization ）

Sketch of laser profile

SHG crystal

Polarization Plate

Cooling Power of Chiller

• Checked the cooling power of chiller is enough or not, even if the water pressure is not enough.

• It was dangerous to use SHG (because of damage to it), used fundamental wave (1064nm)

• Measured the temperature of internal cooling water and the laser power.

• Used Long Pulse Mode （ several hundred us pulse width)

Result of MeasurementCh1(blue) : Water INCh2 (yellow) : Water OUT

• Out temperature exceeds 30 deg C but very stable right after the laser on• Laser power is also stable

Temperature

Laser power

• It seems to be enought with the present chiller.• will discuss with the engineer of the laser company.

Phase Stabilization

Phase Stability

• The drift of the laser phase was observed in long-term measurement.

• The correlation of laser light position (angle) and the laser phase was measured.

• The drift of the laser position was also measured.

• Will the laser phase be stabilized by stabilizing the laser position?

Feedback Stabilization of Position

Mirror with actuator-1

Mirror with actuator-2

PSD1

PSD2

Stabilization of Laser Positionwith stabilization without stabilization

• Long-term drift was stabilized• Shot-term oscillation (several tens of minutes) cannot stabilized.

Phase Stability

• However, the drift of the laser phase is not disappeared even if the laser position was stabilized.

Phase measurement during the position stabilization

Example of phase measurement without position stabilization

• It seems the drift happens at the beginning of the measurement (not DAQ, but the laser light is introduced)

• Also people are around the IP area

IP Target Installation

IP Target Insertion Stage

• Attached on the IP vacuum chamber• Vacuuming test

– No leak was found with vacuum pumped with a rotary pump (2x10-4Pa)

– Stage work normally after the vacuuming

Assembling of IP Target (1)

• Fabrication of the target holder has been finished.

• Assembling

Knife edge target for the laser size measurement at the IP

Assembling of IP Target (2)

• Screen monitor (almina fluorescent plate)

0.1mm thick almina plate

for 174 deg and 2 - 30 deg mode

174 deg mode plate can be seen from the reverse side

Assembling of IP Target (3)

• Attach Φ10μm tungsten wire at the tip of the holder

•　 Stretch the wire and fixed on the holder by soldering•　 3 wires, around 2 mm interval

Nilaco tungsten wire

Installation of Target Holder

• Attach the assembled holder to the mover shaft

Shaft of mover

Alignment of Target• Put a rotating laser just upstream of

Final Doublets and pass through the laser light in the beam pipe to simulate the electron beam path

• Hit the laser light on the screen monitor and adjust the mover axis so that the light is centered on the screen monitor.

• Adjust the CCD camera position so that the light is centered on the image of screen.

• Adjust the focusing and the magnification of camera lens.

Before adjustment After adjustment

Calibration of Axis

• After the alignment, checked the horizontal/vertical axis on the screen.

screen for 174 deg mode screen for 2 - 30 deg mode

Vertical

Horizontal 52 degHorizontal

Vertical

52 deg

Regarding Gamma-ray Detector

Gamma-ray Shutter

• It is desired HVs to the Gamma-ray detector are supplied even if screen monitors and wire scanners are inserted.

• By blocking the collimator hole with lead blocks, shield the detector from a large amount of gamma rays from screen monitors.

Gamma-ray Shutter

• Take out and put in 50x50x200mm lead block in front of collimator

• Can control remotely

Gamma Ray

Move Direction

Layout around Detector

DUMP

Cherenkov Detectorfor Wire Scanner

Front CollimatorLead, Φ20, 200 mm thickness

Movable Collimator in H & VLead, Φ10 or Φ16, 200 mm thickness

Rear CollimatorLead, Φ20, 200 mm thickness

CsI(Tl) Calorimetor

Cherenkov Detector(locally movable)

Movable Background Monitor (Plastic Scintillator with lead plate)

Movable Shutter50x50mm, 200 mm thickness lead block

Lead block shield

BDUMP

Wider chamber

Detector Interlock

• By using gamma-ray shutter, interlock to guard the detector from the large amount gamma rays become simple.– can be done with hardware– reverse interlock won’t be needed

Screen MonitorWire Scanner

Gamma-ray ShutterHV Module

IN

IN

INTERLOCK

contact / noncontact signal