train_dataset.csv

## 1 FILE CONTENTS ############################################# 2101 x 40006 values: - 1 header row, which corresponds to the 40002 resolved wavelengths and 4 element names (Cr, Mn, Mo, and Ni). - 2100 spectra (rows): 50 spectra of 42 distinct targets. <br> Note that the dataset occupies significantly less RAM when loaded than the file's disk sizes (cca. 50 %). <br> Note that the column names may be modified by the software/library used for processing the spectra. Hence, we advise increased caution when extracting the wavelengths. Alternatively, you can use the wavelength values provided separately in the wavelengths.csv file. <br> ## 2 DATA ACQUISITION ############################################# <br> The dataset was collected from metallic targets. Each target's surface was homogenized using a 800 grid sandpaper and cleaned with isopropyl alcohol using paper towels. The targets were sampled at distinct spots in single-shot mode, collecting a single spectrum from each individual spot. There are a total of 50 spectra available for each target. <br> A 1064 nm Nd:YAG laser was used for ablation with a pulse energy of 95 mJ, 10 ns pulse width. The laser pulse was focused into a spot with a diameter of 0.2 mm. <br> The collected emission was resolved with an echelle spectrograph in the 240--1000 nm spectral range (40002 resolved wavelength values), resolving power {\lambda} / {\Delta\lambda} = 6000. <br> The resolved emission was recorded using an EMCCD camera with a 1.5 us delay and 50 us gate width (exposition time). <br> The spectra were not intensity calibrated! This, in combination with the long gate width is part of the challenge.

## 1 文件内容 #############################################
本数据集包含2101行×40006列的数据：
- 1行表头：对应40002个已分辨波长与4种元素名称（铬Cr、锰Mn、钼Mo、镍Ni）。
- 2100条光谱（即数据行）：涵盖42个不同测试靶材，每个靶材对应50条光谱。
> 注意：数据集加载时占用的随机存取存储器（RAM）远小于其磁盘存储容量，仅约为磁盘大小的50%。
> 注意：用于处理光谱的软件或库可能会修改列名，因此在提取波长信息时请格外谨慎。您也可以使用单独存储于wavelengths.csv文件中的波长数值。

## 2 数据采集 #############################################
本数据集采集自金属测试靶材。首先使用800目砂纸对每个靶材表面进行均质化处理，再用浸有异丙醇的纸巾擦拭清洁。随后以单次触发模式在靶材的不同点位进行采样，每个点位采集一条光谱，每个靶材共计采集50条光谱。
实验采用1064 nm Nd:YAG激光器进行烧蚀，其脉冲能量为95 mJ，脉冲宽度为10 ns。激光脉冲经聚焦后形成直径0.2 mm的作用光斑。
采集到的发射光谱经中阶梯光谱仪（echelle spectrograph）在240~1000 nm光谱范围内进行分光分辨，共得到40002个已分辨波长点，光谱分辨率λ/Δλ=6000。
已分辨的发射光谱由电子倍增电荷耦合器件相机（EMCCD）采集，采集时设置1.5 μs的延迟时间与50 μs的门控宽度（即曝光时长）。
所有光谱均未进行强度校准，这一特性与较长的门控宽度共同构成了本数据集的挑战之一。