HRRL radiation tests

Building a new positron beamline in the HRRL cell might require moving the linac itself. R adiation levels were measured on Feb 4, 2009 by M. Balzer and G. Stancari to determine the impact of repositioning the HRRL RF cavity in the accelerator room.

The HRRL was used to accelerate electrons to a 15 MeV beam energy, 20 mA peak current, 1 kHz repetition rate, and 30 ns pulse width. Five OSL dosimeters (For Details on OSL dosimeter, look [[1]]) were placed at each of 15 locations within the cell identified in the sketch below.

Media:dosimeter-locations-20090204.pdf

Readings in mrad are reported in the following table. They were taken before exposure (first column) and after a couple of minutes of machine tuning (second column). Readings in the third column were taken 94 minutes after the second reading. During these 94 minutes, the machine was running with the settings mentioned above.

Media:exposure-measurements-20090204.pdf

Dose rates in mrad/hr at each of the 15 locations can be estimated by subtracting column 2 from column 3, averaging over the 5 dosimeters, and multiplying the result by (60 min/hr) / (94 min). RMS spreads refer to variations within each group of 5.

Location	Dose rate	RMS spread
	(mrad/hr)	(mrad/hr)
1	9	4
2	396	57
3	7940	204
4	2831	117
5	4408	373
6	29339	3332
7	72517	687
8	36507	4746
9	5	5
10	37	4
11	164	40
12	2734	313
13	5828	120
14	7793	2579
15	62431	27155

OSL dosimeters

Dosimeters are placed approximately 1-m off the floor. Large face of the dosimeters were facing HRRL.

Diameter of a dosimeter is measured as:

d = 7.4 mm, 7.6 mm, 7.5 mm, 7.3 mm, 7.3 mm, 7.4 mm, 7.6 mm.

so,

d = 7.44 [math]\pm [/math] 0.13 mm.

Experimental Cell Dose Measurement with HRRL

This experiment is done on 5/17/2010, at 10:00 am.

Dr. Khalid Chouffani wrote the note. Here is photocopy of his note:

page #1

page #2

Detector Used on Channel 16

Link to detector information from producer: [2]

For more detailed information go to: ludlums_Gamma_Area_Monitor_moedl_45-9

16 MeV Beam Energy

Experimental cell measurement with HRRL.

Conditions are:

Rep rate: 40 Hz

Pulse width: 1 [math]\mu sec[/math]

[math]\Delta[/math]E=(10-17) MeV

Peak current of beam (mA)	Energy of beam (MeV)	Measurement on Channel 17, Experimental Cell (mrad)	Measurement on Channel 16, Accelerator cell (mrad)
100	16	4.5 [math]\pm [/math] 0.2	45.5 [math]\pm [/math] 2
69.2	16	4 [math]\pm [/math] 0.2	35, 42.5
60.8	16	3.5 [math]\pm [/math] 0.1	29.2, 28.9
58.0	16	2.8, 2.9	26, 26.7
47.6	16	2.3	19.6, 21.3
33.2	16	1.8, 1.7	14.5, 14.0, 13.7

Beam bear through 1/4 inches diameter collimator with 4 inches lead.

Fit for Channel 16 at 16MeV

Order of the fit	Fit equations	Chi square	p-value
1st order	[math] Dose = (-2.305 \pm 0.095) + (0.511 \pm 0.01)*I_{peak} [/math]	22.38	0.00017

16 MeV Beam Energy

Conditions are:

Rep rate: 40 Hz

Peak current of beam (mA)	Energy of beam (MeV)	Measurement on Channel 17, Experimental Cell (mrad)	Measurement on Channel 16, Accelerator cell (mrad)
136	16	0.3	99.2, 98.7

10 MeV Beam Energy

Conditions are:

Rep rate: 110 Hz

[math]\Delta[/math]E=(8-16) MeV

Peak current of beam (mA)	Energy of beam (MeV)	Measurement on Channel 17, Experimental Cell (mrad)	Measurement on Channel 16, Accelerator cell (mrad)
48.4	10	4.6, 4.7	117.6, 117.5
36.8	10	3.8, 3.9	104.4, 103.5, 102.9
30.8	10	3.1 [math]\pm [/math] 0.1	72.8, 72.9, 72.5
26	10	2.5	56.7, 56.4, 54.6

Fit for channel 17 at 10 MeV

Order of the fit	Fit equations	Chi square	p-value
1st order	[math] Dose = (-0.039 \pm 0.066) + (0.1001 \pm 0.01)*I_{peak} [/math]	0.983	0.6117

Channel 17 Dose Estimation in New Position

Channel 17 is a dose measuring detector on in the HRRL experimental cell.

Calculation

1 rad = 0.01 J/Kg;

Assume that the position 13 at radiation test on Feb 4, 2009 by M. Balzer and G. Stancari will shift to detector position at corner on experiment that is done on 5/17/2010.

Radiation test on Feb 4, 2009 by M. Balzer and G. Stancari used OSL dosimeter.

The area of a OSL dosimeter is:

[math]A_{osl} = 55.3536 \pm 3.0 ~mm^{2} [/math]

Experimental Cell Dose Measurement with HRRL on 5/17/2010 used Ludlums Gamma Area Monitor moedl 45-9 for channel 16. Ludlums Gamma Area Monitor moedl 45-9 has dimension: 7.6 x 25.7 cm (3 x 10.1 in.) (Dia x L).

The area of a Ludlums Gamma Area Monitor moedl 45-9 is:

[math] A_{lgam}=195.32 ~cm^{2} [/math]

The ratio of detectors detecting area is:

[math]\frac{ A_{osl} } {A_{lgam}} = 352.9 \pm 19 [/math]

We assume 100% efficiency for both detectors, their detecting are ratio is their dose ratio.

So, for 15 MeV electron beam, at the corner where we had detector of channel 16, if we moved detector to new position, on the detector of Ludlums Gamma Area Monitor moedl 45-9 we would have dose rate of :

Dose [math] = (352.9 \pm 19) \times 5828 [/math] (mrad/hr)

[math] = 2056701.2 \pm 110 732[/math] (mrad/hr)

[math] = 571.3 \pm 31 [/math] (mrad/sec)

Above dose is created by electron beam of energy 15 MeV and 20 mA peak current.

According to the fit for Channel 16 at 16MeV, for 20 mA of peak current the dose should be:

[math] Dose = (-2.305 \pm 0.095) + (0.511 \pm 0.01)*I_{peak} = (-2.305 \pm 0.095) + (0.511 \pm 0.01)*20 = 1.96 \pm 0.27[/math] (mrad/)

According to the fit for Channel 17 at 10MeV, for 20 mA of peak current the dose should be:

[math] (-0.039 \pm 0.066) + (0.1001 \pm 0.01)*I_{peak} [/math]

The ratio,at 20 mA of peak current, of Channel 16 at 16MeV to Channel 17 at 10MeV is:

[math] \frac{7.915 \pm 0.30}{1.96 \pm 0.27} = 4.03 \pm 0.57 [/math]

Or, the ratio,at 20 mA of peak current, of Channel 17 at 10MeV to Channel 16 at 16MeV is:

[math] \frac{1.96 \pm 0.27}{7.915 \pm 0.30} = 0.248 \pm 0.035 [/math]

Assume proximately same dose rate for 15 MeV and 16 Mev electron beam, so dose rate channel 17 at 10 MeV electron beam is:

[math] \frac{(Dose~Chan17~10MeV)}{(Dose~Chan16~16MeV)} \times (Dose~Chan16~15MeV) \approx {Dose~Chan17~10MeV} [/math]

Which lead to Dose rate of channel 17 at 10 MeV electron and 20 mA peak current:

[math] (0.248 \pm 0.035) \times [/math] [math] 571.3 \pm 31 (mrad/sec) = 142\pm 21[/math]

New Radiation Test

We plan to run another radiation experiment on HRRL. We will place a detector measure dose rate near the corner of wall1,

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