LRF Core Analysis
## LRF Core Analysis

Go to **HETG at XRCF**

### Results and Discussion

(updated 8/11/97)
The results to date suggest adopting the following calibration
values:

Grating | dp/p rms | error | arc min rms | error |

MEG
| 162.
| 50.
| 1.5
| 0.5 |

HEG
| 146.
| 50.
| 1.5
| 0.5 |

For the period variations I have used the sub-assembly value
rss'ed with 100 ppm as an estimate, with an error of +/- 50ppm.

For the roll variations I have used 1.5 arc minute rms
with an error of 0.5 arc minute. This is based on the MEG HSI
FC data set described below which gives a measured
MEG roll rms less than 2.07 arc minute (other effects have not been
removed so this is an upper limit.)

### Analysis chain

#### Sub-assembly Predictions

LR sub-assembly data predicts the values in the table below for
dp/p rms and the grating roll rms values.

Grating | dp/p rms | error | arc min rms | error |

MEG
| 127. ppm
| 10. ppm
| 0.42
| 0.1 |

HEG
| 106. ppm
| 10. ppm
| 0.42
| 0.1 |

The period and dp/p values measured with the LR system should be
accurate - the main additional effect in going to the full flight
model are any period variation effects due to the mounting process
(aligning and screwing the frame to the HESS).

The existence of the "mis-aligned" MEG gratings shows that
the polyimide can introduce polarization effects that can cause
the X-ray roll angle to differ from the polarization-measured
roll angle. The subassembly roll values are the polarization measured
ones. It is possible that the same phenomenon is working
to a smaller degree for all the MEGs and HEGs: polyimide
polarization effects will lead to X-ray roll variations
greater than the sub-assembly predicts.

#### XRCF very preliminary Results

- The 1-D scan data (in Marshall et al. SPIE paper) show the
HRMA-HETG preforming with resolving powers tabulated below:
Grating | Energy | Order | E/dE | dp/p rms limit |

HEG
| 1.254
| 1
| 1049.
| < 405. ppm |

HEG
| 1.254
| 2
| 1418.
| < 300. ppm |

MEG
| 1.254
| 1
| 479.
| < 888. ppm |

MEG
| 1.254
| 3
| 1095.
| < 389. ppm |

### To-do

- There are lots of XRCF data that can be used to improve these values.