作者没有确认。

1实验装置（图2） （演出1小时的第一测量值，以稳定检测器的温度和高压电源之前。） <ol><li>放置在水箱根据治疗头，牢记的SSD将必须增加最多至200厘米。因而油箱应定位低至实现的，这取决于在天花板高度。 </li><li>使水箱与线性加速器（其垂直侧面必须平行于头部的垂直边）。激光可以被用来确保方向是正确的;这个程序是详细的系统的物理引导14。 </li><li>通过执行x和y轮廓测量在两个不同的深度，计算所述光束偏角和使用该头的旋转轴线（参见物理手册）校正验证线性加速器的垂直方向。 </li><li>与遥测配件更换准直器，并用它来ACCUR在78.5厘米SSD ately定位头。附件的尖端刚好触及水面。 </li><li>取下遥测和放置60毫米准直器上的治疗头。 </li><li>用平行于光束方向的圆柱形腔的轴线定位的LIC参考点1.5厘米深的垂直位置， 即得 。这将导致在源和探测器之间80cm的距离。使用激光在光束在横向方向上的中心定位的LIC。 </li><li>放置一个0.125厘米3充满空气电离室（AIC）旁边的LIC，以便能够校正衰减，距离和散射效果。 </li><li>连接LIC和高压电源的静电和设置电压为800 V.连接的AIC到另一个静电和设置电压为400 V。然后等待1小时稳定化的目的。 </li><li>为了保证检测器的侧向定位的准确度，在执行轮廓测量两个横向方向，必要时纠正LIC的零。 </li><li>确保直线加速器的重复速率是固定的（标称值= 150赫兹）。 </li></ol> 2，测量<ol><li>首先，以稳定的LIC响应交付的3000监视单元（MU）的预辐照剂量。然后执行零静电计的。 </li><li>以评估泄漏电流和稳定性，进行了一系列的充电收购与光束截止的时间等于所述测量值（7.5秒，100 MU）的。比较得到与上横梁的测定值的平均值。与波束上测量的最小的值小于0.03％的典型泄漏电荷可忽略不计。 </li><li>将治疗头58.5厘米固态硬盘:使用遥控器在笛卡尔模式，只需在z方向进行20cm的运动。 </li><li>离开治疗室，关上门和编程100亩，在照射操作员控制台。然后启动这两个静电计，提供的剂量，并注意由LIC和工商局测得的费用<img alt="方程（5）" fo:content-width="0.7in" src="/files/ftp_upload/51296/51296eq5.jpg" /> 。 </li><li>重复这个过程10次，以便能够评估统计不确定性。 </li><li>经过十年的测量，进入房间并移动治疗头到下一个位置（68.5厘米SSD）。然后重复步骤2.4和2.5。 </li><li>当磁头移动进一步远离罐的测量点之间的距离可以增大作为电荷改变下列逆平方距离法。 表1提供的测量点的列表的一个例子，随着每个脉冲相应的剂量。 </li></ol><img alt="表1" fo:content-width="6in" src="/files/ftp_upload/51296/51296table1.jpg" style="width: 600px;" /> 表1测量点的两个剂量的列表率的方法（A和B），每个脉冲的相应剂量。 3。分析两种方法可用于分析数据。 方法A <ol><li>对于每一个距离 d，取各测LIC值的比例与在相同距离获得相应的AIC值， <img alt="方程（5）" fo:content-width="0.5in" src="/files/ftp_upload/51296/51296eq12.jpg" /> 。 </li><li>积比率<img alt="方程（5）" fo:content-width="0.5in" src="/files/ftp_upload/51296/51296eq12.jpg" />针对每个脉冲的剂量和使用的线性拟合得到的外推比例为每脉冲零剂量，R 0。 </li><li>与假设收集效率等于1 0毫戈瑞/脉冲，规范所有步骤3.A.1计算的外推值从顺序上一步中得到的f（即规模每比率值的比率一个因素这样使得k R 0 = 1）。 </li><li>绘制f的值对每个脉冲代表的收集效率的演化剂量的值。误差棒可以通过传播来自于每个距离的重复测量评估LIC和AIC费用的不确定性计算。 </li></ol> 方法B <ol><li>就拿比率<img alt="公式6" fo:content-width="0.5in" src="/files/ftp_upload/51296/51296eq6.jpg" />该LIC的读数在AIC的读数为200公分（198.5厘米SSD）和60cm（58.5厘米SSD），并且， <img alt="公式6" fo:content-width="0.5in" src="/files/ftp_upload/51296/51296eq6.jpg" /> 。 </li><li>数值求解下面的方程ü200。 <img alt="公式7" fo:content-width="1.5in" src="/files/ftp_upload/51296/51296eq7.jpg" /></li><li>注入ü200的值在下面的关系式得到的收集效率，F在200厘米的距离。 <img alt="公式8" fo:content-width="1.5in" src="/files/ftp_upload/51296/51296eq8.jpg" /></li><li>的效率可以使用比其它的距离在60cm以内进行计算，只要电荷比是大于3。此过程允许检测的不确定性所计算出的u和的F值。 </li><li>计算参数u为所有测量点，使用以下关系（选择的距离，使<img alt="公式10" fo:content-width="1in" src="/files/ftp_upload/51296/51296eq10.jpg" /> ） <img alt="公式9" fo:content-width="1.5in" src="/files/ftp_upload/51296/51296eq9.jpg" /></li><li>计算所有收集效率，F D，从关系 <img alt="公式11" fo:content-width="1.2in" src="/files/ftp_upload/51296/51296eq11.jpg" /></li><li>绘制f的值对剂量的每脉冲的值，以represe约的收集效率的演变。误差棒可以通过传播来自于每个距离的重复测量评估LIC和AIC费用的不确定性计算。 </li></ol>

<ol>
	<li>Das, I. J., Din, G. X., Ahnesj&#246;, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Small+fields:+non-equlibrium+radiation+dosimetry.">Small fields: non-equlibrium radiation dosimetry.</a> Med. Phys. 35 (1), 206-215 (2008).</li><li>Wickmann, G., Nystrom, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+liquids+in+ionization+chambers+for+high+precision+radiotherapy+dosimetry.">The use of liquids in ionization chambers for high precision radiotherapy dosimetry.</a> Phys. Med. Biol. 37 (9), 1789-1812 (1992).</li><li>Chung, E., Soisson, E., Seuntjens, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dose+homogeneity+specification+for+reference+dosimetry+of+nonstandard+fields.">Dose homogeneity specification for reference dosimetry of nonstandard fields.</a> Med. Phys. 39 (1), 407-414 (2011).</li><li>Francescon, P., Kilby, W., Satariano, N., Cora, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monte+Carlo+simulated+correction+factors+for+machine+specific+reference+field+dose+calibration+and+output+factor+measurement+using+fixed+and+iris+collimators+on+the+Cyberknife+system.">Monte Carlo simulated correction factors for machine specific reference field dose calibration and output factor measurement using fixed and iris collimators on the Cyberknife system.</a> Phys. Med. Biol. 57 (12), 3741-3758 (2012).</li><li>Wagner, A., Crop, F., Lacornerie, T., Vandevelde, F., Reynaert, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+a+liquid+ionization+chamber+for+stereotactic+radiotherapy+dosimetry.">Use of a liquid ionization chamber for stereotactic radiotherapy dosimetry.</a> Phys. Med. Biol. 58 (8), 2445-2459 (2013).</li><li>Johansson, B., Wickman, G., Bahar-Gogani, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=General+collection+efficiency+for+liquid+iso-octane+and+tetramethylsilane+in+pulsed+radiation.">General collection efficiency for liquid iso-octane and tetramethylsilane in pulsed radiation.</a> Phys. Med. Biol. 42 (10), 1929-1938 (1997).</li><li>Andersson, J., T&#246;lli, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+the+two-dose-rate+method+for+general+recombination+correction+for+liquid+ionization+chambers+in+continuous+beams.">Application of the two-dose-rate method for general recombination correction for liquid ionization chambers in continuous beams.</a> Phys. Med. Biol. 56 (2), 299-314 (2010).</li><li>Sjgren, R., Wendelsten, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+two-dose-rate+method+for+general+recombination+correction+for+liquid+ionization+chambers+in+pulsed+beams.">A two-dose-rate method for general recombination correction for liquid ionization chambers in pulsed beams.</a> Phys. Med. Biol. 55 (15), 4247-4260 (2010).</li><li>Boag, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ionization+measurements+at+very+high+intensities:+part+I.+Pulsed+radiation+beams.">Ionization measurements at very high intensities: part I. Pulsed radiation beams.</a> Br. J. Radiol. 23 (274), 601-611 (1950).</li><li>Boag, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+saturation+curve+for+ionization+measurements+in+pulsed+radiation+beams.">The saturation curve for ionization measurements in pulsed radiation beams.</a> Br. J. Radiol. 25 (300), 649-650 (1952).</li><li>Stewart, K. J., Elliott, A., Seuntjens, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+guarded+liquid+ionization+chamber+for+clinical+dosimetry.">Development of a guarded liquid ionization chamber for clinical dosimetry.</a> Phys. Med. Biol. 52 (11), 3089-3104 (2007).</li><li>Yin, Z., Hugtenburg, R. P., Beddoe, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Response+corrections+for+solid-state+detectors+in+megavoltage+photon+dosimetry.">Response corrections for solid-state detectors in megavoltage photon dosimetry.</a> Phys. Med. Biol. 49 (11), 3691-3702 (2004).</li><li>Griessbach, I., Lapp, M., Bohsung, J., Gademann, G., Harder, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dosimetric+characteristics+of+a+new+unshielded+silicon+diode+and+its+application+in+clinical+photon+and+electron+beams.">Dosimetric characteristics of a new unshielded silicon diode and its application in clinical photon and electron beams.</a> Med. Phys. 32, 3750-3754 (2005).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Accuray Inc., Physics Essentials Guide P/N 032515A-ENG. Accuray Inc. , (2010).</li></ol>

作者什么都没有透露。

上面介绍的方法允许在评估一个LIC的复合效应在大范围内剂量率（0.14〜1.58毫戈瑞/脉冲）的。方法A是简单的，但比B方法，它提供了收集效率，女的相当准确的（绝对）值更多的不确定性有关。重组是负责在信号约2％的损耗在整个范围内调查，但这个范围比在常规测量什么，通常跨越较大。在输出因素的最大误差为0.35％，并达到1％的百分深度剂量测量的结果部分被证明。 用于进行协议的关键要素是在实验的初始设置，因为所有的测量是相对于治疗头的初始位置进行。因此，人们应注意初始SSD的精确测量，以便能够与探测器的读数为每每脉冲剂量。这也适用于放置在水中探测器;应注意，该有效测量点（位于1毫米入射窗在microLion检测器的情况下，后面）被定位在1.5厘米表面的下方。在1小时的延迟和预辐照剂量也是必不可少的，以便稳定在800 V电源和温度。 直线加速器的重复率直接影响每脉冲剂量。在800 MU /分钟，以150赫兹的频率，每个脉冲的剂量为0.89毫戈瑞/脉冲。这个频率应该是固定的所有测量，以确定的距离上具有每脉冲剂量的影响是唯一的变量因素。该方法可以以连续的束的一些适应7的情况下被使用。在该处的SSD不能直接移动该治疗头而变化的其他设备中，重复率可以被修改，以引入每个脉冲变化的剂量。如果此参数为固定为好，在SSD仍然可以通过移动LIC和水表面在罐修改，但这种方法的精度可能比在本研究中所用的治疗头移动更低。 在LIC中，其在小剂量学领域使用的鉴定用于下一步骤是调查诱导的反应，如在检测器和音量效果的材料（扰动的其他因素，即一个事实，即敏感体积不比较小的光束的尺寸）。这是可能通过使用Monte Carlo模拟5。以考虑到这些方面，全局校正因子可以以充分消除扰动应用到临床常规测量获得的LIC读数（输出因子，百分深度剂量时，剂量分布）。 这些perturbating效果的完整的特性和校正后，t他LIC可以作为一个额外的检测器，用于小束剂量，允许访问，百分深度剂量和由其它检测器测得的输出因子的独立验证。其极高的在纵向方向上的空间分辨率也将适用于矩形域的剂量，只有一个小的尺寸（ 例如断层放疗）。

使用气体电离室已经执行多年剂量在放射治疗。这些探测器表现良好，据"传统"放射治疗而言， 即大齐（或缓慢变化）领域中使用。然而，最近的许多设备，如射波刀（ 图1）系统研究了在这项工作中，能够使用非常小的领域（下至5mm）的可能性。其他设备产生高度调制的光束分布，如在调强放射治疗（IMRT）。常规充气探测器不能很好地适合于这些技术1;为了达到可接受的空间分辨率的所述腔体的容积就必须减少到一个尺寸，其中所述腔室的反应会变得过低。二极管提供更小的敏感体积的优势，而且它们在小束剂量广泛使用。但是他们提出其他限制，例如散射效应从他们所产生的金属屏蔽12,13。 在液体电离室2（LIC），电离密度要高得多，因此，敏感体积的减少是可能的而不会影响检测器的响应。此外，该敏感介质具有接近于水的密度，从而降低了空气腔室相关联的积分通量扰动。这些方面使LIC的小束剂量3-5一个有趣的候选人。 仍有一些问题能够进行日常剂量测量与低收入国家之前解决。首先，由于较高的电离密度的复合效果比在充满空气的腔室6-8更重要。重组可以是初始（电子重新结合，其母亲离子）或一般（两种离子从不同的电离事件来重组）。后者是依赖于剂量率入射到探测器上;吨他的手段是相对剂量测量（ 即剂量分布，百分深度剂量输出因子）有可能发生的偏差是由于剂量率的变化。重组的特征是一般的收集效率，定义为测量电荷的比例由入射辐射所产生的电荷和逸出初始重组:F = Q C / Q 0。在气体检测器的重组效果是使用从BOAG 9,10的理论，而不能在低收入国家11施加两个电压的方法进行评价。 另一种可以在使用两个剂量率的方法08包括不同的剂量率以隔离一般性重组的影响，并通过测量有关的一般的收集效率的发现 <img alt="式（1）" fo:content-width="1in" src="/files/ftp_upload/51296/51296eq1.jpg" /> 其中 u是DEF作为独立非执行董事 <img alt="公式2" fo:content-width="1in" src="/files/ftp_upload/51296/51296eq2.jpg" />用α作为复合系数，Q 0电荷的逃逸初始重组，h为电极分离的量，e为基本电荷，V腔室的敏感体积中，k 1和k 2的正电荷和负电荷的迁移率，和U所施加的电压。通过在每个脉冲的不同剂量的测量能够获得参数u，从而收集效率，F。每个脉冲的剂量是由关系式给出 <img alt="式（3）" fo:content-width="3in" src="/files/ftp_upload/51296/51296eq3.jpg" />所有的测量都在射波刀的参考条件下进行（源表面距离的SSD =78.5厘米，1.5厘米深，60毫米准直器）。使用大的准直异体WS避免与小束相关的容积效应。给定的剂量率是800 MU /分钟，重复频率为150赫兹，这导致在0.89毫戈瑞/脉冲（在参考条件下，1 MU对应1 cGy的剂量）的剂量。当脉冲重复频率保持恒定，每个脉冲的剂量不仅取决于剂量率在格雷/分钟，这是通过逆平方距离法相关的SSD: <img alt="公式4" fo:content-width="1in" src="/files/ftp_upload/51296/51296eq4.jpg" /> 对于两个SSD D 1和D 2。

<table border="0" cellpadding="0" cellspacing="0" width="788">
	<tbody>
		<tr>
			<td>MicroLion chamber</td>
			<td>PTW</td>
			<td>31018</td>
			<td>http://www.ptw.de/2263.html</td>
		</tr>
		<tr>
			<td>Unidos Webline dosimeter</td>
			<td>PTW</td>
			<td></td>
			<td>http://www.ptw.de/unidos_webline_dosemeter_rt0.html</td>
		</tr>
		<tr>
			<td>HV supply</td>
			<td>PTW</td>
			<td></td>
			<td>http://www.ptw.de/2265.html</td>
		</tr>
		<tr>
			<td>MP3 water scanning system</td>
			<td>PTW</td>
			<td></td>
			<td>http://www.ptw.de/2032.html</td>
		</tr>
		<tr>
			<td>0.125 cm3 SemiFlex chamber</td>
			<td>PTW</td>
			<td>31010</td>
			<td>http://www.ptw.de/semiflex_chambers0.html?&#38;cId=6069</td>
		</tr>
		<tr>
			<td>Cyberknife</td>
			<td>Accuray</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

characterization of recombination effects in a liquid ionization chamber used for the dosimetry of a radiosurgical accelerator

大多数现代放射治疗设备允许使用非常小的领域，无论是通过在调强放射治疗（IMRT）的子束或通过立体定向放射治疗，其中定位精度可以提供非常高的剂量每部分在小体积的病人。医疗加速器剂量学测量用充气电离室按常规实现。然而，在小束这些受到不可忽视的扰动效应。本研究着重于液体电离室，它提供的空间分辨率和低通量扰动方面的优势。离子复合效应进行了研究与射波刀系统（爱可）使用的microLion检测器（PTW）。该方法包括在不同的源 - 表面的距离进行一系列的水箱的测量，并应用修正的基础上同时气体检测器测量的液体检测器的读数。这种方法facilitaTES分离从液体培养基敏感的高密度而产生和获得校正因子应用到检测器读数的复合效果。主要的困难在于在设置于能够检测到在腔室中的反应小的变化实现的精度足够的水平。

在图3中的方法A得到的收集效率f的暗算每个脉冲的剂量，取值范围为0〜1.6毫戈瑞/脉冲凡在信号中的2％的损失就可以看出。的各点遵循线性行为。误差棒显示重要的不确定性，似乎固有的方法，可以大大减少与使用方法B的还值得一提的是，在这个方法的AIC响应被假定为没有进行重组的影响，这并不一定是完全正确的。要验证这一点我们可以简单地进行单独使用AIC中积聚帽（无水箱），正确的距离平方倒数类似的测量;小的偏差可以被观察到，并列入的不确定性值。 图4示出了从第二方法（B）计算出的收集效率。它证明了更精确的和具有提供的f的绝对值的优势。德维从线性行为ations都很小，在信号的损失比同方法A略低作为直接应用方法B的因子，可以计算以校正一般重组在每个脉冲在给定的剂量，通过简单地把收集效率，f的倒数。然后这些因素可以应用于相对深度剂量测量。 图5显示了前和后的重组校正用的二极管（未受到重组的影响），并与LIC测量的相对深度剂量。时的曲线归一化在240毫米（其中复合效应消失）的深度，它们一致，这意味着该修正补偿复合效应在堆积区（其中，每个脉冲的剂量，因此，校正因子是最高的）。这表明，所计算的校正因子是准确的，可以作为两个剂量率的方法的验证。 图1:射波刀系统正。用于测量射波刀系统，与加速器头部朝下的看法。水箱可以被放置在地板上，或在机器人榻在房间的后面可见，取决于头以上的可用空间。 <img alt="图2" src="/files/ftp_upload/51296/51296fig2highres.jpg" /> 图2的实验装置的设置是在这里所表示的AIC和LIC置于彼此相邻的水箱（1.5厘米深）内，在光束，这是向下的中心。箭头指示每个系列的测量值之间的加速器的头部运动，开始在60厘米的距离（58.5厘米SSD），并在200公分（198.5厘米SSD）结束。 图3。总收集效率，方法A的总收集效率，F，相对于每脉冲剂量的进化的图形（在毫戈瑞/脉冲）由方法A得到的<img alt="图4" src="/files/ftp_upload/51296/51296fig4highres.jpg" /> 图4。总除尘效率 ​​，方法B.一般除尘效率 ​​暗算每个脉冲的剂量，从以下方法B的结果<img alt="图5" fo:content-width="5in" src="/files/ftp_upload/51296/51296fig5highres.jpg" width="500" /> 图5。应用到相对深度剂量测量。从二极管的测量中获得的相对深度剂量以蓝色显示。从LIC测量的结果是由红（未校正）和黄色（校正）曲线来表示。 <a href="https://www.jove.com/files/ftp_upload/51296/51296fig5highres.jpg" target="_blank">请点击此处查看该图的放大版本。</a>

Watch this Scientific Journal Video about Characterization of Recombination Effects in a Liquid Ionization Chamber Used for the Dosimetry of a Radiosurgical Accelerator at JoVE.com

Characterization of Recombination Effects in a Liquid Ionization Chamber Used for the Dosimetry of a Radiosurgical Accelerator

越来越多的放射治疗设备通过提供非常小的光束传递的剂量对肿瘤的优势，不但可提高整合和每分次高剂量。许多不同的检测器可用于这些小域的剂量。在本研究中，离子的重组的影响进行了研究用于使用立体定向放射治疗系统的液体电离室。

重组的影响在液体电离室表征用于一个电波加速器的剂量学

Most modern radiation therapy devices allow the use of very small fields, either through beamlets in Intensity-Modulated Radiation Therapy (IMRT) or via ...

characterization-recombination-effects-liquid-ionization-chamber-used

Research

JoVE Journal

Engineering

11.7K 次观看.  Centre Oscar Lambret. 越来越多的放射治疗设备通过提供非常小的光束传递的剂量对肿瘤的优势，不但可提高整合和每分次高剂量。许多不同的检测器可用于这些小域的剂量。在本研究中，离子的重组的影响进行了研究用于使用立体定向放射治疗系统的液体电离室。 

视频: Characterization of Recombination Effects in a Liquid Ionization Chamber Used for the Dosimetry of a Radiosurgical Accelerator

Ultrasound Velocity Measurement in a Liquid Metal Electrode

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently more difficult than measuring the flow of a transparent fluid, since optical methods are not applicable. Ultrasound can be used to measure the velocity of an opaque fluid, not only at isolated points, but at hundreds or thousands of points arrayed along lines, with good temporal resolution. When applied to a liquid metal electrode, ultrasound velocimetry involves additional challenges: high temperature, chemical activity, and electrical conductivity. Here we describe the experimental apparatus and methods that overcome these challenges and allow the measurement of flow in a liquid metal electrode, as it conducts current, at operating temperature. Temperature is regulated within &#177;2 &#176;C using a Proportional-Integral-Derivative (PID) controller that powers a custom-built furnace. Chemical activity is managed by choosing vessel materials carefully and enclosing the experimental setup in an argon-filled glovebox. Finally, unintended electrical paths are carefully prevented. An automated system logs control settings and experimental measurements, using hardware trigger signals to synchronize devices. This apparatus and these methods can produce measurements that are impossible with other techniques, and allow optimization and control of electrochemical technologies like liquid metal batteries.

Ultrasound velocimetry is used to study mixing by fluid flow in liquid metal electrodes. The focus of this manuscript is to illustrate the methods used for making precise, spatially-resolved ultrasound measurements while limiting oxidation and controlling and monitoring temperature, applied current, and the heater power being supplied.

超声速度测量的液态金属电极

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently ...

科研

工程学

Electron Channeling Contrast Imaging for Rapid III-V Heteroepitaxial Characterization

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging (ECCI) in a scanning electron microscope (SEM). ECCI allows for imaging of defects and crystallographic features under specific diffraction conditions, similar to that possible via plan-view transmission electron microscopy (PV-TEM). A particular advantage of the ECCI technique is that it requires little to no sample preparation, and indeed can use large area, as-produced samples, making it a considerably higher throughput characterization method than TEM. Similar to TEM, different diffraction conditions can be obtained with ECCI by tilting and rotating the sample in the SEM. This capability enables the selective imaging of specific defects, such as misfit dislocations at the GaP/Si interface, with high contrast levels, which are determined by the standard invisibility criteria. An example application of this technique is described wherein ECCI imaging is used to determine the critical thickness for dislocation nucleation for GaP-on-Si by imaging a range of samples with various GaP epilayer thicknesses. Examples of ECCI micrographs of additional defect types, including threading dislocations and a stacking fault, are provided as demonstration of its broad, TEM-like applicability. Ultimately, the combination of TEM-like capabilities &#8211; high spatial resolution and richness of microstructural data &#8211; with the convenience and speed of SEM, position ECCI as a powerful tool for the rapid characterization of crystalline materials.

The use of electron channeling contrast imaging in a scanning electron microscope to characterize defects in III-V/Si heteroexpitaxial thin films is described. This method yields similar results to plan-view transmission electron microscopy, but in significantly less time due to lack of required sample preparation.

电子通道造影的快速III-V异质特征

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging ...

Phase Diagram Characterization Using Magnetic Beads as Liquid Carriers

Magnetic beads with ~1.9 &#181;m average diameter were used to transport microliter volumes of liquids between contiguous liquid segments with a tube for the purpose of investigating phase change of those liquid segments. The magnetic beads were externally controlled using a magnet, allowing for the beads to bridge the air valve between the adjacent liquid segments. A hydrophobic coating was applied to the inner surface of the tube to enhance the separation between two liquid segments. The applied magnetic field formed an aggregate cluster of magnetic beads, capturing a certain liquid amount within the cluster that is referred to as carry-over volume. A fluorescent dye was added to one liquid segment, followed by a series of liquid transfers, which then changed the fluorescence intensity in the neighboring liquid segment. Based on the numerical analysis of the measured fluorescence intensity change, the carry-over volume per mass of magnetic beads has been found to be ~2 to 3 &#181;l/mg. This small amount of liquid allowed for the use of comparatively small liquid segments of a couple hundred microliters, enhancing the feasibility of the device for a lab-in-tube approach. This technique of applying small compositional variation in a liquid volume was applied to analyzing the binary phase diagram between water and the surfactant C12E5 (pentaethylene glycol monododecyl ether), leading to quicker analysis with smaller sample volumes than conventional methods.

Here, we present a protocol to investigate multi-component phase diagrams using externally controlled magnetic beads as liquid carriers in a lab-in-tube approach. This approach can aid in applications that seek to gather further information on phase change in complex liquid systems.

相图表征使用磁珠用作液体载体

Magnetic beads with ~1.9 &#181;m average diameter were used to transport microliter volumes of liquids between contiguous liquid segments with a tube for ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

检测和钯的回收，从城市矿山黄金和钴金属使用标有纳米货车车轮形的孔隙新型传感器/吸附剂

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and non-destructively reveals the hydrogen density distribution at surfaces, at interfaces, and in the volume of solid materials with high depth resolution. The technique applies a 15N ion beam of 6.385 MeV provided by an electrostatic accelerator and specifically detects the 1H isotope in depths up to about 2 &#956;m from the target surface. Surface H coverages are measured with a sensitivity in the order of ~1013 cm-2 (~1% of a typical atomic monolayer density) and H volume concentrations with a detection limit of ~1018 cm-3 (~100 at. ppm). The near-surface depth resolution is 2-5 nm for surface-normal 15N ion incidence onto the target and can be enhanced to values below 1 nm for very flat targets by adopting a surface-grazing incidence geometry. The method is versatile and readily applied to any high vacuum compatible homogeneous material with a smooth surface (no pores). Electrically conductive targets usually tolerate the ion beam irradiation with negligible degradation. Hydrogen quantitation and correct depth analysis require knowledge of the elementary composition (besides hydrogen) and mass density of the target material. Especially in combination with ultra-high vacuum methods for in-situ target preparation and characterization, 1H(15N,&#945;&#947;)12C NRA is ideally suited for hydrogen analysis at atomically controlled surfaces and nanostructured interfaces. We exemplarily demonstrate here the application of 15N NRA at the MALT Tandem accelerator facility of the University of Tokyo to (1) quantitatively measure the surface coverage and the bulk concentration of hydrogen in the near-surface region of a H2 exposed Pd(110) single crystal, and (2) to determine the depth location and layer density of hydrogen near the interfaces of thin SiO2 films on Si(100).

We illustrate the application of 1H(15N,&#945;&#947;)12C resonant nuclear reaction analysis (NRA) to quantitatively evaluate the density of hydrogen atoms on the surface, in the volume, and at an interfacial layer of solid materials. The near-surface hydrogen depth profiling of a Pd(110) single crystal and of SiO2/Si(100) stacks is described.

通过与核反应分析深度剖面的表面和界面层和颗粒材料氢含量的定量

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and ...

Electrochemical Etching and Characterization of Sharp Field Emission Points for Electron Impact Ionization

A new variation of the drop-off method for fabricating field emission points by electrochemically etching tungsten rods in a NaOH solution is described. The results of studies in which the etching current and the molarity of the NaOH solution used in the etching process were varied are presented. The investigation of the geometry of the tips, by imaging them with a scanning electron microscope, and by operating them in field emission mode is also described. The field emission tips produced are intended to be used as an electron beam source for ion production via electron impact ionization of background gas or vapor in Penning trap mass spectrometry applications.

A method for electrochemically etching field emission tips is presented. Etching parameters are characterized and the operation of the tips in field emission mode is investigated.

电化学腐蚀和电子碰撞电离夏普场发射点的表征

A new variation of the drop-off method for fabricating field emission points by electrochemically etching tungsten rods in a NaOH solution is described. ...

Testing of Nanoparticle Release from a Composite Containing Nanomaterial Using a Chamber System

With the rapid development of nanotechnology as one of the most important technologies in the 21st century, interest in the safety of consumer products containing nanomaterials is also increasing. Evaluating the nanomaterial release from products containing nanomaterials is a crucial step in assessing the safety of these products, and has resulted in several international efforts to develop consistent and reliable technologies for standardizing the evaluation of nanomaterial release. In this study, the release of nanomaterials from products containing nanomaterials is evaluated using a chamber system that includes a condensation particle counter, optical particle counter, and sampling ports to collect filter samples for electron microscopy analysis. The proposed chamber system is tested using an abrasor and disc-type nanocomposite material specimens to determine whether the nanomaterial release is repeatable and consistent within an acceptable range. The test results indicate that the total number of particles in each test is within 20% from the average after several trials. The release trends are similar and they show very good repeatability. Therefore, the proposed chamber system can be effectively used for nanomaterial release testing of products containing nanomaterials.

Nanoparticle release is tested using a chamber system that includes a condensation particle counter, an optical particle counter and sampling ports to collect filter samples for microscopy analysis. The proposed chamber system can be effectively used for nanomaterial release testing with a repeatable and consistent data range.

从使用室系统一个复合含纳米材料的纳米颗粒释放测试

With the rapid development of nanotechnology as one of the most important technologies in the 21st century, interest in the safety of consumer products ...

Measurement of Outgassing Rates of Steels

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of steels meet the criterion of low outgassing required for high or ultrahigh vacuum applications. However, a given material can present different outgassing rates depending on its manufacturing process or the various pretreatment processes involved during the fabrication. Thus, the measurement of outgassing rates is highly desirable for a specific vacuum application. For this reason, the rate-of-pressure rise (RoR) method is often used to measure the outgassing of hydrogen after bakeout. In this article, a detailed description of the design and execution of the experimental protocol involved in the RoR method is provided. The RoR method uses a spinning rotor gauge to minimize errors that stem from outgassing or the pumping action of a vacuum gauge. The outgassing rates of two ordinary steels (stainless steel and mild steel) were measured. The measurements were made before and after the heat pretreatment of the steels. The heat pretreatment of steels was performed to reduce the outgassing. Extremely low rates of outgassing (on the order of 10&#8722;11 Pa m3 sec&#8722;1 m&#8722;2) can be routinely measured using relatively small samples.

A protocol for the measurement of outgassing rates of hydrogen from ordinary steel vacuum chambers using the rate-of-pressure rise method is presented.

钢的出气率的测量

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of ...

Spark Plasma Sintering Apparatus Used for the Formation of Strontium Titanate Bicrystals

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with one twist grain boundary. This apparatus utilizes high uniaxial pressure and a pulsed direct current for rapid consolidation of material. Diffusion bonding of strontium titanate bicrystals without fracture, in a spark plasma sintering apparatus, is possible at high pressures due to the unusual temperature dependent plasticity behavior of strontium titanate. We demonstrate a method for the successful formation of bicrystals at accelerated time scales and lower temperatures in a spark plasma sintering apparatus compared to bicrystals formed by conventional diffusion bonding parameters. Bond quality was verified by scanning electron microscopy. A clean and atomically abrupt interface containing no secondary phases was observed using transmission electron microscopy techniques. Local changes in bonding across the boundary was characterized by simultaneous scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy.

A viable technique for the formation of strontium titanate bicrystals at high pressure and fast heating rate via the spark plasma sintering apparatus is developed.

放电等离子烧结设备中使用的钛酸锶双晶体的形成

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with ...

Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials such as organo-lead halide perovskites is presented. The perovskite film thickness and absorption coefficient are initially characterized by profilometry and UV-VIS absorption spectroscopy. Calibration of both laser power and cavity sensitivity is described in detail. A protocol for performing Flash-photolysis Time Resolved Microwave Conductivity (TRMC) experiments, a non-contact method of determining the conductivity of a material, is presented. A process for identifying the real and imaginary components of the complex conductivity by performing TRMC as a function of microwave frequency is given. Charge carrier dynamics are determined under different excitation regimes (including both power and wavelength). Techniques for distinguishing between direct and trap-mediated decay processes are presented and discussed. Results are modelled and interpreted with reference to a general kinetic model of photoinduced charge carriers in a semiconductor. The techniques described are applicable to a wide range of optoelectronic materials, including organic and inorganic photovoltaic materials, nanoparticles, and conducting/semiconducting thin films.

A Time Resolved Microwave Conductivity technique for investigating direct and trap-mediated recombination dynamics and determining carrier mobilities of thin film semiconductors is presented here.

通过时间分辨微波电导率重组动力学薄膜光伏材料

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials ...