HESSI SHUTTER PARAMETERS

 

The purpose of this document is to summarize the as-built parameters of the HESSI shutters.

 

There are 'thin' and 'thick' shutters associated with each subcollimator. Each shutter was fabricated from an aluminum disk, which was machined by Tecomet to form 3 concentric circular subareas of different thicknesses. The shutter parameters are slightly different for each subcollimator due both to fabrication tolerances and due to different design parameters. (The differences were required in order to minimize any spatial coherence between the shutter geometry and the grids.) Nevertheless the overall goal was to have roughly similar transmissions for all subcollimators.

 

The primary objective of the shutter calibration was to determine the surface density of each subarea of each shutter. The calibration was based on 5 types of data.

  1. The OGCF was used to confirm that the diameters of the subareas on each shutter matched their nominal values.
  2. The XGCF was used to measure the transmission of the shutters for Fe55 and Cd109 sources (6 and 23 keV respectively). In each case the sources were collimated to a beam of about 10 mm diameter which was directed at the center of the shutter. Cd109 data was also taken with the beam restricted to the outer area.
  3. The thicknesses of the outer and middle areas were measured mechanically.
  4. Radiographs were taken of the inner area to confirm that thickness variations were sufficiently small that they could be neglected.
  5. Each shutter was accurately weighed so that the average surface density could be determined directly.

 

Analysis of the calibration data yielded the individual shutter parameters (diameters and surface densities) shown in the table below. Also tabulated is the diameter of the graded-Z guard ring which defines the effective diameter of the front segment of each detector.

For each individual shutter, the diameters were converted to the fraction of available area corresponding to each subarea (3 per shutter). When both shutters are IN, there are effectively 5 subareas, whose fractional area and combined surface density was also calculated. The fractional area and surface density for each subarea, attenuator setting and subcollimator are tabulated in the boxed area in the 'Attenuator Parameter Table'. The boxed area was copied to a text file ( APT_yyyymmdd.txt where yyyymmdd is the version date) and is included in \ssw\hessi\dbase\spec_resp.

 

During data analysis, the latest version of the attenuator parameter table is used by the function, hsi_shutter_transmission, to calculate the attenuator transmission as a function of energy, subcollimator and attenuator state. This calculation uses log-log interpolation of the NIST tables for aluminum which are read by the function, read_mat_xcom.

 

Plots of shutter transmission as a function of energy are shown in Figures 1 and 2 for a typical subcollimator. (These plots are normalized so that both attenuators OUT would give 1 and so do not include the effect of blankets, etc. The dotted, dashed and dot-dashed lines correspond to THIN, THICK and THIN+THICK cases respectively.)

Corresponding plots of the effective radius (relative to the graded-Z ring) of the transmitting area is shown in Figure 3, which illustrates that at low energies, all the transmission is through the innermost area.

 

There are two approaches by which in-flight data can be used to confirm the shutter transmission. First, the continuity of semi-calibrated light curves when a shutter inserted or removed can be checked as a function of energy. Second, ratios of semi-calibrated spectra among detectors can be compared with and without attenuators, again as a function of energy. If significant anomalies are found, the in-flight data can be combined with prelaunch calibration data to improve the attenuator parameter table so that the updated calibration can be applied retroactively to the existing flare database.

 


 

HESSI ATTENUATOR PARAMETER TABLE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

2

3

4

5

6

7

8

9

 

Graded-Z ring diameter

mm

 

58.5

58.5

57.5

58.5

58.5

58.5

57.5

58.5

58.5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Shutter ID

 

 

A1-1

A2

A3

A4

A5-1

A6

A7-1

A8

A9-1

 

Inner diameter

mm

 

1.716

1.716

1.716

1.716

1.940

1.716

2.050

1.940

3.360

 

Middle diameter

mm

 

24.300

24.300

24.300

24.300

24.300

24.300

24.300

24.300

24.300

 

Inner surface density

g/cm2

 

0.0133

0.0135

0.0134

0.0127

0.0153

0.0133

0.0162

0.0156

0.0262

 

Middle surface density

g/cm2

 

0.177

0.179

0.178

0.178

0.154

0.179

0.153

0.151

0.166

 

Outer surface density

g/cm2

 

0.414

0.412

0.415

0.415

0.389

0.414

0.391

0.391

0.397

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Shutter ID

 

 

B1-1

B2

B3

B1-3

B5

B6

B7

B8

B9-1

 

Inner diameter

mm

 

6.743

6.743

6.743

6.743

6.743

6.743

6.743

6.743

6.15

 

Middle diameter

mm

 

17.1

17.1

17.1

17.1

17.1

17.1

17.1

17.1

17.1

 

Inner surface density

g/cm2

 

0.0192

0.0191

0.0189

0.0188

0.0188

0.0187

0.0187

0.0185

0.0208

 

Middle surface density

g/cm2

 

0.261

0.260

0.257

0.262

0.262

0.257

0.262

0.256

0.260

 

Outer surface density

g/cm2

 

0.112

0.112

0.110

0.114

0.114

0.107

0.115

0.109

0.114

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Conversion to ssw Attenuator parameter table format

 

 

 

 

 

 

 

 

 

LABEL

 

 

APT1-1

 

 

 

 

 

 

 

 

 

VERSION-DATE

 

 

6-Jun-01

 

 

 

 

 

 

 

 

 

DESCRIPTION

 

 

GH: Preflight CBE of shutter parameters, from XGCF data, nominal diameters, 25-apr-01 calib analysis, updated ring diam

 

fraction1

detector-middleB

THIN

0.9146

0.9146

0.9116

0.9146

0.9146

0.9146

0.9116

0.9146

0.9146

 

fraction2

middleB-innerB

THIN

0.0722

0.0722

0.0747

0.0722

0.0722

0.0722

0.0747

0.0722

0.0744

 

fraction3

innerB

THIN

0.01329

0.01329

0.01375

0.01329

0.01329

0.01329

0.01375

0.01329

0.01105

 

fraction4

0

THIN

0

0

0

0

0

0

0

0

0

 

fraction5

0

THIN

0

0

0

0

0

0

0

0

0

 

Surf.Density1

outerB

THIN

0.1120

0.1119

0.1105

0.1140

0.1138

0.1068

0.1153

0.1088

0.1142

 

Surf.Density2

middleB

THIN

0.2611

0.2596

0.2571

0.2621

0.2617

0.2567

0.2618

0.2564

0.2605

 

Surf.Density3

innerB

THIN

0.0192

0.0191

0.0189

0.0188

0.0188

0.0187

0.0187

0.0185

0.0208

 

Surf.Density4

0

THIN

0

0

0

0

0

0

0

0

0

 

Surf.Density5

0

THIN

0

0

0

0

0

0

0

0

0

 

fraction1

detector-middleA

THICK

0.8275

0.8275

0.8214

0.8275

0.8275

0.8275

0.8214

0.8275

0.8275

 

fraction2

middleA-innerA

THICK

0.1717

0.1717

0.1777

0.1717

0.1714

0.1717

0.1773

0.1714

0.1692

 

fraction3

innerA

THICK

0.000860

0.000860

0.000891

0.000860

0.001100

0.000860

0.001271

0.001100

0.003299

 

fraction4

0

THICK

0

0

0

0

0

0

0

0

0

 

fraction5

0

THICK

0

0

0

0

0

0

0

0

0

 

Surf.Density1

outerA

THICK

0.4143

0.4125

0.4150

0.4150

0.3894

0.4137

0.3907

0.3908

0.3972

 

Surf.Density2

middle A

THICK

0.1770

0.1792

0.1775

0.1778

0.1542

0.1794

0.1534

0.1513

0.1656

 

Surf.Density3

innerA

THICK

0.0133

0.0135

0.0134

0.0127

0.0153

0.0133

0.0162

0.0156

0.0262

 

Surf.Density4

0

THICK

0

0

0

0

0

0

0

0

0

 

Surf.Density5

0

THICK

0

0

0

0

0

0

0

0

0

 

fraction1

detector-middleA

THICK+THIN

0.8275

0.8275

0.8214

0.8275

0.8275

0.8275

0.8214

0.8275

0.8275

 

fraction2

middleA-middleB

THICK+THIN

0.0871

0.0871

0.0902

0.0871

0.0871

0.0871

0.0902

0.0871

0.0871

 

fraction3

middleB-innerB

THICK+THIN

0.0722

0.0722

0.0747

0.0722

0.0722

0.0722

0.0747

0.0722

0.0744

 

fraction4

innerB-innerA

THICK+THIN

0.01243

0.01243

0.01286

0.01243

0.01219

0.01243

0.01248

0.01219

0.00775

 

fraction5

innerA

THICK+THIN

0.000860

0.000860

0.000891

0.000860

0.001100

0.000860

0.001271

0.001100

0.003299

 

Surf.Density1

outerA+outerB

THICK+THIN

0.5263

0.5244

0.5254

0.5289

0.5032

0.5206

0.5060

0.4995

0.5114

 

Surf.Density2

middleA+outerB

THICK+THIN

0.2890

0.2911

0.2880

0.2918

0.2680

0.2862

0.2687

0.2600

0.2798

 

Surf.Density3

middleA+middleB

THICK+THIN

0.4381

0.4388

0.4346

0.4400

0.4159

0.4361

0.4151

0.4076

0.4261

 

Surf.Density4

MiddleA+innerB

THICK+THIN

0.1963

0.1983

0.1964

0.1966

0.1730

0.1981

0.1721

0.1698

0.1863

 

Surf.Density5

innerA+innerB

THICK+THIN

0.0326

0.0326

0.0323

0.0315

0.0340

0.0320

0.0350

0.0341

0.0470

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Comments:

6-Jun-01

 

Graded-Z ring diameters corrected per DS memo.

 

 

 

 

 

 

 

APT1-1 is the current best estimate preflight version of the attenuator parameter table.

 

 

 

 

 

 

 

Boxed area should be pasted into a text file named 'label.txt' which is read by hsi_rd_shutter_parameters.