未设置Powershell ACL

我试图将ACL设置为仅修改，但当我运行它运行的代码时，指定用户的权限仍然为空，我哪里出错了

$ApplicationPoolIdentity = "domain\username"

function SetACL()
{
    param (
        [Parameter(Mandatory=$true)]
        [string]        $Path 
    )

    $Acl = Get-Acl $Path
    Write-Host "Path:" $Path "ID:" $ApplicationPoolIdentity
    $Ar = New-Object  system.security.accesscontrol.filesystemaccessrule($ApplicationPoolIdentity,"Write","Allow")
    $Acl.SetAccessRule($Ar)
    Write-Host $Acl
    $Acl | Set-Acl $Path
}

SetACL "F:\Test123\"

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此代码正在我的系统上运行。：我想可能是权限之类的。。但不会返回错误