HLab meeting

2/17/09

K. Shirotori

Contents

• Noise reduction for CYRIC experiment

Purpose• To measure polarization of proton

(Scifi-MPPC システムを用いた陽子陽子散乱断面積測定と左右非対称度の測定 )

– p+12C → 12C+ppol

⇒ ppol+12C→12C+pscat

⇒ pscat measured

⇒LS force effect

• Test MPPC + Scifi active target• Study for us (staff, students)

Necessary to noise reduction• MPPC gain is small : ~105

– Planned to use PMT amplifier

⇒The noise is enhanced by PMT amp, too.– Difficulty of one photon separation from pedestal– Energy resolution– Common noise Accidental trigger, Gomi data⇒

• Weak point of detector system– Ground of bias circuit– Protection of electromagnetic wave

No cover of bias circuit Flat cable between bias circuit and MPPC

– Hand made…?

Basic concept

• Ground : Same ground level– Detectors, crates, electric circuit, HV

• Clear cabling– As simple as possible (beautiful cabling)

• Insulation– No ground loop

• Shield for weak points– Al foil method for flat cables

Environment at TR4• Noise source : Cyclotron magnet, RF, beam line magnet,

vacuum pump, compressor, electric power supply…⇒Cannot be removed.*~20 kHz switching noise from cyclotron magnet +

• All system (detector, electronics, cables) in Target room4⇒To connect all ground to be same by ground ribbon*Ground loop

• Need to connect beam pipe (target vacuum chamber) to electronics– AC100V between beam pipe and electronics (floating ground)

⇒Beam pipe to be ground or other common ground*Nose from Cyclotron

• Ground of electronics power supply is unknown.⇒Not used*Not used for Hyperball2 experiment(Ground loop or some noise appeared and switching noise ~20kHz)

• Ground rod in target room4 is connected to the beam pipe.⇒Not used*Not effective reduction for Hyperball2 situation and risk of ground loop

Target room4

Target room4Beam pipe

Shield

Vacuum chamber

Beam from Cyclotrons

Frame (isolated from floor)

Bias circuit

(Yaki-niku, Kameki-sushi)

Detector

(Scifi, MPPC)

AC100V

DAQ PC

NIM

VME

Distribution board

Turbo pump

Unknown : Distribution board ground, beam line ground, beam line power supply, any untouchable device

Hole

Bias circuit

▼

1 M

▼

1 M

▼

1 M

0.1 F 0.1 F 0.1 F

MPPC

Bias HV

PMT amp PMT amp PMT amp

Set up principle • Connect beam pipe to electronics

– Shut out the risk of AC100V (Ground rod in target room4 is connected to the beam pipe)

– Ground of electronics power supply is unknown. Not used⇒

• Connect between bias circuit and NIM&VME circuit by ground ribbon

• Carefully check the insulation (ground loop by lemo i-connector)

• Try and error around bias circuit (flat cable shielding, to connect beam line and lemo-connector by ground ribbon)

Set up

NIM

VMEFrame

Vacuum

chamber

Beam line

AC100V

Cable (lemo)

Cable (flat)

Floor

Ground

Upstream of beam line

Connected

Disconnected

??

??

Electronics

⇒Frame ground

by ground ribbon

Target room4Beam pipe

Shield

Vacuum chamber

Beam from Cyclotrons

Frame (isolated from floor)

Bias circuit

(Yakiniku, Kameki-sushi)

Detector

(Scifi, MPPC)

AC100V

DAQ PC

NIM

VME

Distribution board

Cable (lemo)

Cable (flat)

Turbo pump

Tako-ashi

Unknown : Distribution board ground, beam line ground, beam line power supply, unknown device

Hole

Ground of bias circuit

▼

1 M

▼

1 M

▼

1 M

0.1 F 0.1 F 0.1 F

MPPC

Bias HV

PMT amp PMT amp PMT amp

Lemo

Common ground

⇒Beam line

Lemo

Frame

Flat cable (covered Al foil)

Ground ribbon

Ground

ribbon

Ground of bias circuit

▼

1 M

▼

1 M

▼

1 M

0.1 F 0.1 F 0.1 F

MPPC

Bias HV

PMT amp PMT amp PMT amp

Lemo

Common ground

⇒Beam line

Lemo

Frame

Flat cable (covered Al foil)

Ground ribbon

Ground

ribbon

Noise reduced

Noise : 20 kHz (switching)

+ (maybe ground loop)

One photon (after PMT map)

: ~3 mV

Noise : 20 mV 1~2 mV⇒(~2 mV @ Ge room)

• 理由強固なグラウンド : 同相成分の除去Cabling : No ground loop

アルミ作戦 : ケーブルの遮蔽とグラウンド強化

Sample of noise (almost reduced)

To be continued ….

圧縮

Before After