Experimental Study of the BEPC BackgroundsⅡ

JIN Da-PengIHEP, Beijing, China

Representing the Backgrounds Study GroupMay 11, 2007, BEPC IMAC MeetingⅡ

Outline

Motivation

Radiation detectors arrangement

Preliminary results

Next to do

Motivation1. Take means to protect the detectors from being

damaged

2. Provide good environment for data taking

BEPC is going wellⅡ

Radiation Detectors Arrangement

75cm

1#

2#

3#

4#

5#

2. 22m

6#

3. 31m

1. 65m1. 65m

PI N Di odesRadFETs

30cm

10cm10cm10cm

0#1#2#

3#

4#

10cm10cm

40cm

e+ e-

5#6#7#

Z

X

Y

X

Y

X

Y Y

X

Magnified View

Fork PipeBoth Beams

e- Beam

On Mar. 27, 2007, 2# was moved to 5#

Detectors in the right places

Parameters of theRadiation Detectors

• PIN Diodes– 0.25nA/mrad·s-1

– Damage: 1~10nA/krad– Temp Dep: 1.11times/oC– Accuracy: ~5mrad/s

• RadFETs– Range: 20,000rad– Accuracy: 1.5rad– Freq: 10min

Preliminary Results1#, 2#, 3#, 4# : 75cm from the IP; 6# : 3.31m from the IP.

160nA

80nA

Preliminary Results5# : 2.22m from the IP.

3000nA

More than

1000nA

Preliminary Results

5# detector suffers much more radiation doses than the others, which is more than one fold.

Dominated doses for

5# detector are from the

electron beam.

1#, 2#, 3#, 4# : 75cm from the IP; (Both beams)

6# : 3.31m from the IP; (Upper stream of e-)

5# : 2.22m from the IP. (Upper stream of e-)

Preliminary Results Electron Beam Tuning

1#, 2#, 3#, 4# : 75cm from the IP; 6# : 3.31m from the IP.

Preliminary Results Electron Beam Tuning

5# : 2.22m from the IP.

Preliminary Results Electron Beam Tuning

Dose rates during injections are much higher than steady runs for each detector.

Injections Steady Runs

Dose Rate

(mrad/s)Tens to Hundr

ends0.5 to

about Ten

Int. Dose

(rad/day)

About 100 rad (4#) to

Several Thousands (5#)

Preliminary Results Positron Beam Tuning

0

20

40

60

80

100

120 1# 2# 3# 4# 6#

e+.Curr e－.Curr

Dose Rate

Do

se R

ate

/ n

A

Be

am

Cu

rre

nt /

mA

Time

06:00:002007-03-10

12:00:002007-03-102007-03-10

00:00:00 00:00:002007-03-11

18:00:002007-03-10

0

10

20

30

40

1#, 2#, 3#, 4# : 75cm from the IP; 6# : 3.31m from the IP.

Preliminary Results Positron Beam Tuning

5# : 2.22m from the IP.

1300

1400

1500

1600 5#

e+.Curr e－.Curr

Dose Rate

Do

se R

ate

/ n

A

Be

am

Cu

rre

nt /

mA

Time

06:00:002007-03-10

12:00:002007-03-102007-03-10

00:00:00 00:00:002007-03-11

18:00:002007-03-10

0

10

20

30

40

Preliminary Results Positron Beam Tuning

5# and 6# detectors suffers less doses.

Vertical detectors suffers less doses.

For the horizontal detectors 1# and 3#, Outer Ring(1#) .GT. Inner Ring(3#)

Preliminary Results Double Beam Tuning

0

100

200

300

400

500

600

700 Dose Rate

Curr of e－

Curr of e+

Dose Rate of 2# PIN Diode

Do

se R

ate

/ n

A

Be

am

Cu

rre

nt /

mA

Time00:00:00

2007-03-2812:00:00

2007-03-2800:00:00

2007-03-2912:00:00

2007-03-29

0

10

20

30

40

50

60

70

2# moved to 5#.

Preliminary Results Double Beam Tuning

2# moved to 5#.

Preliminary Results Double Beam Tuning

2# moved to 5#.

Really, Dose Rate at the fork pipe (about 2.2m from the IP) is much higher.

Preliminary Results Int. Dose to the CsI Crystals

0

5

10

15

20

25

30

35

Int.D

ose

/ ra

d

RadFET 0#

RadFET 1#

RadFET 2#

RadFET 3#

Curr of e+

Curr of e－

Int Dose of RadFET at e- Up Stream

Time

00:00:002007-03-28

12:00:002007-03-28

00:00:002007-03-29

12:00:002007-03-29

0

10

20

30

40

50

60

70

Be

am

Cu

rre

nt /

mA

30cm

40cm

50cm

60cm

Preliminary Results Int. Dose to the CsI Crystals

40cm

50cm

60cm

0

5

10

15

RadFET 5#

RadFET 6#

RadFET 7#

Curr of e－

Curr of e+

Int Dose of RadFET at e+ Up Stream

0

10

20

30

40

50

60

70

Int.D

ose

/ ra

d

Be

am

Cu

rre

nt /

mA

00:00:002007-03-28

12:00:002007-03-28

00:00:002007-03-29

12:00:002007-03-29

Preliminary Results Int. Dose to the CsI Crystals

The maximum Int. dose at the position of the inner most CsI crystals is about 10rads/day, which is about 10 times that of the design value.

Injections bring much more doses.

The total Int. dose from the electron beam is higher than that from the positron beam.

Preliminary Results Int. Dose at the fork pipe

0

1000

2000

3000

4000

5000

Int Dose

Curr of e－

Curr of e+

Time

Int.D

ose

/ ra

d

00:00:002007-03-28

12:00:002007-03-28

00:00:002007-03-29

12:00:002007-03-29

Int Dose of RadFET 4#

0

10

20

30

40

50

60

70

Be

am

Cu

rre

nt /

mA

Preliminary Results Int. Dose at the fork pipe

In the previous measurement, the Int. dose is .GT. 3000rads/day, which is mainly due to e- injections.

In some cases, one turn injections can bring hundrends to one thousand rads Int. doses.

Preliminary Results Beam Loss Monitors

IPNo. 48 No. 72

BLMs are sensitive with charged particles

e+ e-

Preliminary Results Beam Loss Monitors

Preliminary Results Beam Loss Monitors

Preliminary Results Beam Loss Monitors

Preliminary Results Beam Loss Monitors

Why so high dose?

The accelerator needs to be well tuned, since we have just started.

In the currently used vacuum chambers, the radius near the fork pipe is smaller than the design values and makes here the bottleneck of the storage ring.

Collimators not installed.

Next to do

Further understand the results from the PIN Diodes, FETs and BLMs;

Deal with the backgrounds seriously and push ahead the manufacture and installation of the collimators;

Your suggestions???

Thanks!